HUAWEI S9300 Terabit Routing Switch network switch Troubleshooting - IP Service

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Quidway S9300 Terabit Routing Switch

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Troubleshooting - IP Service

Issue

Date

2010-07-15

HUAWEI TECHNOLOGIES CO., LTD.

No part of this document may be reproduced or transmitted in any form or by any means without prior written consent of Huawei Technologies Co., Ltd.

Trademarks and Permissions

and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.

All other trademarks and trade names mentioned in this document are the property of their respective holders.

Notice

The purchased products, services and features are stipulated by the contract made between Huawei and the customer. All or part of the products, services and features described in this document may not be within the purchase scope or the usage scope. Unless otherwise specified in the contract, all statements, information, and recommendations in this document are provided "AS IS" without warranties, guarantees or representations of any kind, either express or implied.

The information in this document is subject to change without notice. Every effort has been made in the preparation of this document to ensure accuracy of the contents, but all statements, information, and recommendations in this document do not constitute the warranty of any kind, express or implied.

Huawei Technologies Co., Ltd.

Address: Huawei Industrial Base

Bantian, Longgang

Shenzhen 518129

People's Republic of China

Website:

Email: http://www.huawei.com

[email protected]

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Troubleshooting - IP Service About This Document

About This Document

Intended Audience

This document describes the process of troubleshooting the IP address, and UDP Helper, and provides typical troubleshooting cases.

l l l l

This document is intended for:

Network planning engineers

Hardware installation engineers

Commissioning engineers

Data configuration engineers

Symbol Conventions

The symbols that may be found in this document are defined as follows.

Symbol

DANGER

Description

Indicates a hazard with a high level of risk, which if not avoided, will result in death or serious injury.

Indicates a hazard with a medium or low level of risk, which if not avoided, could result in minor or moderate injury.

WARNING

TIP

NOTE

CAUTION

Indicates a potentially hazardous situation, which if not avoided, could result in equipment damage, data loss, performance degradation, or unexpected results.

Indicates a tip that may help you solve a problem or save time.

Provides additional information to emphasize or supplement important points of the main text.

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Command Conventions

The command conventions that may be found in this document are defined as follows.

Convention

Boldface

Italic

[ ]

{ x | y | ... }

[ x | y | ... ]

{ x | y | ... }

[ x | y | ... ]

&<1-n>

Description

The keywords of a command line are in boldface.

Command arguments are in italics.

Items (keywords or arguments) in brackets [ ] are optional.

Optional items are grouped in braces and separated by vertical bars. One item is selected.

Optional items are grouped in brackets and separated by vertical bars. One item is selected or no item is selected.

Optional items are grouped in braces and separated by vertical bars. A minimum of one item or a maximum of all items can be selected.

Optional items are grouped in brackets and separated by vertical bars. Several items or no item can be selected.

The parameter before the & sign can be repeated 1 to n times.

A line starting with the # sign is comments.

Change History

Changes between document issues are cumulative. Therefore, the latest document issue contains all changes made in previous issues.

Changes in Issue 01 (2010-07-15)

Initial commercial release.

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About This Document...................................................................................................................iii

1 IP Addressing Troubleshooting..............................................................................................1-1

1.1 IP Addressing Overview.................................................................................................................................1-2

1.1.1 Classification of IP Addresses................................................................................................................1-2

1.1.2 IP Address Unnumbered........................................................................................................................1-5

1.1.3 References..............................................................................................................................................1-5

1.2 Configuring the IP Address of an Interface Troubleshooting.........................................................................1-5

1.2.1 Typical Networking................................................................................................................................1-5

1.2.2 Configuration Notes...............................................................................................................................1-6

1.2.3 Troubleshooting Flowchart....................................................................................................................1-6

1.2.4 Troubleshooting Procedure....................................................................................................................1-7

1.3 Configuring the IP Address Unnumbered of an Interface Troubleshooting...................................................1-8

1.3.1 Typical Networking................................................................................................................................1-8

1.3.2 Configuration Notes...............................................................................................................................1-8

1.3.3 Troubleshooting Flowchart....................................................................................................................1-9

1.3.4 Troubleshooting Procedure....................................................................................................................1-9

1.4 Troubleshooting Cases..................................................................................................................................1-10

1.4.1 Can not Borrow an IP Address.............................................................................................................1-11

2 DHCP Troubleshooting............................................................................................................2-1

2.1 Introduction to DHCP.....................................................................................................................................2-2

2.1.1 DHCP Server..........................................................................................................................................2-2

2.1.2 DHCP Relay...........................................................................................................................................2-3

2.1.3 DHCP Proxy...........................................................................................................................................2-3

2.1.4 Procedure for Obtaining the IP Address from the DHCP Server or the DHCP Relay Agent................2-4

2.1.5 DHCP Proxy Procedure.........................................................................................................................2-6

2.2 Troubleshooting of the DHCP Server Based on the Global Address Pool.....................................................2-7

2.2.1 Typical Networking................................................................................................................................2-7

2.2.2 Configuration Notes...............................................................................................................................2-8

2.2.3 Troubleshooting Flowchart....................................................................................................................2-9

2.2.4 Troubleshooting Procedure..................................................................................................................2-11

2.3 DHCP Relay Troubleshooting......................................................................................................................2-12

2.3.1 Typical Networking..............................................................................................................................2-12

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2.3.2 Configuration Notes.............................................................................................................................2-13

2.3.3 Troubleshooting Flowchart..................................................................................................................2-13

2.3.4 Troubleshooting Procedure..................................................................................................................2-14

2.4 Troubleshooting Cases..................................................................................................................................2-15

2.4.1 IP Address Assigned by the DHCP Server to a DHCP Client Conflicts with That of Another DHCP Client

.......................................................................................................................................................................2-15

2.4.2 DHCP Client Cannot Obtain an IP Address from the DHCP Server...................................................2-17

2.4.3 DHCP Client Cannot Obtain an IP Address Through the DHCP Relay Agent...................................2-18

3 DHCPv6 Troubleshooting........................................................................................................3-1

3.1 DHCPv6 Relay Troubleshooting.................................................................................................................... 3-2

3.1.1 Troubleshooting Flowchart....................................................................................................................3-2

3.1.2 Troubleshooting Procedure....................................................................................................................3-4

3.2 Troubleshooting Cases....................................................................................................................................3-5

3.2.1 Clients Cannot Obtain IPv6 Addresses Through DHCPv6 Relay......................................................... 3-5

4 UDP Helper Troubleshooting..................................................................................................4-1

4.1 UDP Helper Overview....................................................................................................................................4-2

4.2 UDP Helper Troubleshooting..........................................................................................................................4-2

4.2.1 Typical Networking................................................................................................................................4-2

4.2.2 Configuration Notes...............................................................................................................................4-3

4.2.3 Troubleshooting Flowchart....................................................................................................................4-4

4.2.4 Troubleshooting Procedure....................................................................................................................4-5

4.3 Troubleshooting Cases....................................................................................................................................4-6

4.3.1 UDP Packets Cannot Be Relayed to the Destination Server..................................................................4-6

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Figures

Figure 1-1 Five IP address classes.......................................................................................................................1-2

Figure 1-2 Typical Networking diagram of IP address configuration on an interface.........................................1-6

Figure 1-3 Troubleshooting flowchart of IP addressing......................................................................................1-6

Figure 1-4 Typical networking diagram of IP address unnumbered configuration on an interface.....................1-8

Figure 1-5 Troubleshooting flowchart of IP address unnumbered.......................................................................1-9

Figure 1-6 Networking diagram of IP address unnumbered..............................................................................1-11

Figure 2-1 Typical networking diagram of the DHCP server..............................................................................2-2

Figure 2-2 Typical networking diagram of the DHCP relay agent......................................................................2-3

Figure 2-3 Typical networking diagram of DHCP proxy....................................................................................2-4

Figure 2-4 Procedure for obtaining the IP address from the DHCP server or the DHCP relay agent.................2-5

Figure 2-5 DHCP proxy procedure......................................................................................................................2-6

Figure 2-6 Typical networking of the DHCP server............................................................................................2-8

Figure 2-7 Troubleshooting flowchart of the DHCP server based on the global address pool..........................2-10

Figure 2-8 Typical networking of DHCP relay..................................................................................................2-12

Figure 2-9 Troubleshooting flowchart of DHCP relay......................................................................................2-14

Figure 2-10 Conflict of the IP addresses obtained from the DHCP server........................................................2-16

Figure 2-11 Networking where a DHCP client cannot obtain an IP address from the DHCP server................2-17

Figure 2-12 Networking where a DHCP client cannot obtain an IP address through the DHCP relay agent

.............................................................................................................................................................................2-18

Figure 3-1 DHCPv6 relay troubleshooting flowchart..........................................................................................3-3

Figure 3-2 Networking where clients cannot obtain IPv6 addresses...................................................................3-6

Figure 4-1 Typical networking diagram of the UDP helper.................................................................................4-2

Figure 4-2 UDP helper troubleshooting flowchart...............................................................................................4-5

Figure 4-3 Networking diagram of the UDP helper.............................................................................................4-7

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Troubleshooting - IP Service Tables

Tables

Table 1-1 Classification and range of IP addresses..............................................................................................1-3

Table 1-2 Some special IP addresses....................................................................................................................1-4

Table 1-3 Private IP addresses..............................................................................................................................1-5

Table 1-4 Error prompts and the corresponding ways to rectify the faults..........................................................1-7

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Troubleshooting - IP Service 1 IP Addressing Troubleshooting

IP Addressing Troubleshooting

About This Chapter

Describes the knowledge related to IP address troubleshooting, including IP address overview, troubleshooting flowchart and troubleshooting procedure in a typical networking, troubleshooting cases.

1.1 IP Addressing Overview

Describes the knowledge you need to know before troubleshooting the IP addressing.

1.2 Configuring the IP Address of an Interface Troubleshooting

Describes the notes about IP addressing, and provides the relevant troubleshooting flowchart and the troubleshooting procedure in a typical networking for IP addressing.

1.3 Configuring the IP Address Unnumbered of an Interface Troubleshooting

Describes the notes about IP address unnumbered, provides the relevant troubleshooting flowchart and the troubleshooting procedure in a typical networking for IP address unnumbered.

1.4 Troubleshooting Cases

This section presents several troubleshooting cases.

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1.1 IP Addressing Overview

Describes the knowledge you need to know before troubleshooting the IP addressing.

1.1.1 Classification of IP Addresses

1.1.2 IP Address Unnumbered

1.1.3 References

1.1.1 Classification of IP Addresses

To communicate with each other in an IP network, each host on the network must be assigned an IP address. If you want to connect a computer to the Internet, you need to apply an IP address from the Internet Service Provider (ISP). An IP address has 32 bits, composed of the following two parts: l l

Network ID field (net-ID): It is applied to distinguish networks. The first bits of the net-ID are called the class field (or class bits). These bits are used to distinguish the IP address classes.

Host ID field (host-ID): It is applied to distinguish different hosts on the network.

Five IP Address Classes

As shown in

Figure 1-1

, IP addresses are further classified into five classes to facilitate IP

address management and networking. You can judge the class of an IP address through the first bits in the network ID field.

Figure 1-1 Five IP address classes

0 Net-id

1 0 Net-id

C 1 1 0

D 1 1 1 0

E 1 1 1 1

Host-id

Net-id

Multicast-address

Reserved

Host-id

1-2

At present, the commonly adopted IP addresses are Class A, Class B, and Class C addresses.

Class D addresses are multicast addresses. Addresses in Class E are reserved. For detailed description of IP address classification. Refer to RFC 1166.

Some IP addresses are reserved for particular purposes, and they cannot be applied by common users.

Table 1-1

lists the ranges of IP addresses for all five classes.

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Table 1-1 Classification and range of IP addresses

Class Address

Range

A 0.0.0.0 to

127.255.255.25

Available IP

Network Range

1.0.0.0 to

126.0.0.0

Description

The IP addresses with host IDs as all 0s are network addresses, and are used for network routing.

The IP addresses with host IDs as all 1s are broadcast addresses, that is, the broadcast to all hosts on the network.

The IP address 0.0.0.0 is used only for temporary communication during system start-up in the Dynamic Host

Configuration Protocol (DHCP) mode. It cannot be an effective destination address.

The IP address with network IDs as 0s represents the current network, which indicates that the device can use the current network even if it does not know the network ID of the network.

The IP addresses with the network ID in the format of 127.X.Y.Z are reserved for the loopback test. The packets sent to these addresses will not be outputted to the network. The packets are processed internally and considered as input packets.

B 128.0.0.0 to

191.255.255.25

128.1.0.0 to

191.254.0.0

192.0.0.0 to

223.255.255.25

192.0.1.0 to

223.255.254.0

None

The IP addresses with host IDs as all 0s are network addresses, and are used for network routing.

The IP addresses with host IDs as all 1s are broadcast addresses, that is, the broadcast to all hosts on the network.

The IP addresses with host IDs as all 0s are network addresses, and are used for network routing.

The IP addresses with host IDs as all 1s are broadcast addresses, that is, the broadcast to all hosts on the network.

The addresses in Class D are multicast addresses.

224.0.0.0 to

239.255.255.25

240.0.0.0 to

255.255.255.25

None The addresses are reserved for future use.

The IP address 255.255.255.255 is used as the LAN broadcast address.

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Special IP Addresses

In actual applications, some special IP addresses exist. See

Table 1-2

to find their ranges and

description.

Table 1-2 Some special IP addresses

Networ k ID

All 0s -

Subnet

Host ID

All 0s

Source

Address

All 0s

127

All 1s net-id net-id net-id

subnetid

All 1s

Host ID

Any value

All 1s.

All 1s

Never

Destination

Address

Never

Description

Never

This kind of addresses is applied to the hosts on the network.

This kind of addresses is applied to the specified hosts on the network.

This kind of addresses is applied to the loopback addresses.

This kind of addresses is applied to the limited broadcasts (never forwarded).

This kind of addresses is applied to send broadcast packets to the network specified by the net-id.

This kind of addresses is applied to send broadcast packets to the subnets specified by the net-id and subnet-id.

This kind of addresses is applied to send broadcast packets to all subnets specified by the net-id.

NOTE

net-id and subnet-id indicate that the corresponding fields that are neither all 0s nor all 1s.

Private IP Addresses

To solve the problem of IP address shortage, the concept of private IP address is introduced.

Private addresses indicate the IP addresses of internal networks or hosts. These IP addresses can only be used in the internal network, rather than the public network. Three IP address segments reserved for the private network are described in RFC 1918. The organization responsible for

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IP address allocation reserves the following IP addresses as the private network addresses. See

Table 1-3

for details:

Table 1-3 Private IP addresses

Network Classification

Address Range

10.0.0.0 to 10.255.255.255

172.16.0.0 to 172.31.255.255

192.168.0.0 to 192.168.255.255

1.1.2 IP Address Unnumbered

IP Address Unnumbered can be applied in the following scenario: An interface has no IP address; then it can utilize the IP address of another interface. The main purpose of IP address unnumbered is to save IP address resources.

An interface without an IP address cannot generate routes and forward packets. IP address unnumbered, in essence, is to utilize an interface without the IP address being configured, by

"borrowing" an IP address from another interface.

1.1.3 References

l l

For more information on IP addresses, refer to the following documents:

RFC 1166: Internet Numbers

RFC 1918: Address Allocation for Private Internets

1.2 Configuring the IP Address of an Interface

Troubleshooting

Describes the notes about IP addressing, and provides the relevant troubleshooting flowchart and the troubleshooting procedure in a typical networking for IP addressing.

1.2.1 Typical Networking

1.2.2 Configuration Notes

1.2.3 Troubleshooting Flowchart

1.2.4 Troubleshooting Procedure

1.2.1 Typical Networking

Figure 1-2

shows the typical networking diagram of IP address configuration on an interface.

Troubleshooting IP addressing is based on this diagram.

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Figure 1-2 Typical Networking diagram of IP address configuration on an interface

GE1/0/0

VLANIF10

10.1.1.1

GE1/0/0

VLANIF10

10.1.1.2

Internet

SwitchA

SwitchB

1.2.2 Configuration Notes

Item

Configuring an IP address

Notes

To configure the IP address for an interface, you need to configure the

IP address and the subnet mask at the same time.

To configure an IP address, run the ip address ip-address mask command in the interface view.

1.2.3 Troubleshooting Flowchart

As to the networking diagram shown in

1.2.1 Typical Networking

, if the following error

prompts are displayed, perform based on the flowchart in

Figure 1-3

Figure 1-3 Troubleshooting flowchart of IP addressing

IP addressing on an interface fails

A prompt is displayed?

Yes

Find a solution according to the displayed prompt

Is fault rectified?

Yes

End

Seek technical support

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1.2.4 Troubleshooting Procedure

Procedure

Step 1 Check the error prompts and find the corresponding ways to rectify the faults.

Table 1-4 Error prompts and the corresponding ways to rectify the faults

Error Prompt

Error: The specified IP address is invalid.

Error: The number of addresses of the specified interface reached the upper limit (32).

Error: Please delete the sub address in the interface view first.

Description

The prompt indicates that the IP address is invalid.

The IP address or the subnet mask may be wrongly configured. Then reconfigure the IP address.

Error: The specified address conflicts with another address.

Error: The specified primary address does not exist.

Error: Please configure the primary address in the interface view first.

The prompt indicates that IP addresses conflict. The

IP address conflict is caused by the repetitious use of the IP address by another interface in the device.

Please configure a different IP address.

The prompt indicates that the specific primary IP address to be deleted does not exist.

The prompt indicates that the secondary IP address cannot be configured. Once IP address unnumbered is configured, the secondary IP address cannot be configured.

The prompt indicates that the number of secondary

IP addresses on an interface exceeds the maximum, and no more secondary IP address can be configured.

The prompt indicates that the primary IP address cannot be deleted. Before the deletion of a primary IP address, delete all secondary IP addresses on the interface.

Error: The specified address cannot be deleted because it is not the primary address of this interface.

Error: The specified sub address does not exist.

Error: The address already exists.

The prompt indicates that the secondary IP address cannot be deleted.

The secondary IP address cannot be deleted through the command of the primary IP address deletion. Run the command of the secondary IP address deletion.

The prompt indicates that the specific secondary IP address to be deleted does not exist.

A repetitious secondary IP address is on the interface.

Configure a different secondary IP address.

Step 2 No above prompt appears, but you fail to configure the IP address on the interface successfully.

Then contact Huawei technical personnel.

----End

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1.3 Configuring the IP Address Unnumbered of an Interface

Troubleshooting

Describes the notes about IP address unnumbered, provides the relevant troubleshooting flowchart and the troubleshooting procedure in a typical networking for IP address unnumbered.

1.3.1 Typical Networking

1.3.2 Configuration Notes

1.3.3 Troubleshooting Flowchart

1.3.4 Troubleshooting Procedure

1.3.1 Typical Networking

Figure 1-4

shows the typical networking diagram of IP address unnumbered. Troubleshooting

IP address unnumbered is based on this diagram.

Figure 1-4 Typical networking diagram of IP address unnumbered configuration on an interface

SwitchB

SwitchA

Tunnel

SwitchC

PC1

PC2

1.3.2 Configuration Notes

Item

Configuring IP address unnumbered

Notes

The Ethernet interface cannot borrow the IP address from another interface.

The interface with a borrowed IP address has no IP address. So, no route can be configured for it. The devices should be configured manually to achieve the interconnection between devices.

To configure IP address unnumbered, run the ip address

unnumbered interface interface-type interface-number command in the interface view.

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1.3.3 Troubleshooting Flowchart

As to the networking diagram shown in

1.3.1 Typical Networking

, if you find any fault in IP

address unnumbered configuration, perform based on the flowchart in

Figure 1-5

Figure 1-5 Troubleshooting flowchart of IP address unnumbered

Fail to borrow an

IP address

Is IP address unnumbered configured?

Yes

Configure IP address unnumbered on the interface

Assign an IP address to the specified interface

Specified interface has an

IP address?

Yes

Seek technical support

Is the fault rectified?

Yes

Is the fault rectified

Yes

End

1.3.4 Troubleshooting Procedure

Procedure

Step 1 Check whether IP address unnumbered is configured on the interface.

In the interface view, run the display this command to check whether IP address unnumbered is configured on the interface. The following is an example:

[S9300A-Tunnel9/0/1] display this

# interface Tunnel9/0/1

ip address unnumbered interface LoopBack0

If IP address unnumbered is not configured, enable the function on the interface.

Step 2 Check whether the interface that needs to lend the IP address has an IP address.

In the interface view, run the display ip interface command to check whether an IP address is configured on the interface. The following is an example:

[S9300A-Tunnel9/0/1] display ip interface LoopBack 0

LoopBack0 current state : UP

Line protocol current state :UP (spoofing)

The Maximum Transmit Unit : 1500 bytes input packets : 0, bytes : 0, multicasts : 0

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Troubleshooting - IP Service output packets : 0, bytes : 0, multicasts : 0

Internet Address is 1.1.1.1/32

Broadcast address : 1.1.1.1

TTL invalid packet number: 0

ICMP packet input number: 0

Echo reply: 0

Unreachable: 0

Source quench: 0

Routing redirect: 0

Echo request: 0

Router advert: 0

Router solicit: 0

Time exceed: 0

IP header bad: 0

Timestamp request: 0

Timestamp reply: 0

Information request: 0

Information reply: 0

Netmask request: 0

Netmask reply: 0

Unknown type: 0

If no IP address is configured, configure an IP address on the interface.

Step 3 Check whether information about IP address unnumbered on the interface is correct.

In the interface view, run the display_this_interface command to check whether the interface can be configured with the IP address unnumbered. The following is an example:

[S9300A-Tunnel9/0/1] display this interface

Tunnel9/0/1 current state : UP

Line protocol current state : DOWN

Description:HUAWEI, Quidway Series, Tunnel9/0/1 Interface

Route Port,The Maximum Transmit Unit is 1500

Internet Address is unnumbered, using address of LoopBack0(1.1.1.1/32)

Encapsulation is TUNNEL, loopback not set

Tunnel protocol is NONE

300 seconds input rate 0 bits/sec, 0 packets/sec

300 seconds output rate 0 bits/sec, 0 packets/sec

0 seconds input rate 0 bits/sec, 0 packets/sec

0 seconds output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes

0 input error

0 packets output, 0 bytes

0 output error

Input:

Unicast: 0 packets, Multicast: 0 packets

Output:

Unicast: 0 packets, Multicast: 0 packets

Input bandwidth utilization : --

Output bandwidth utilization : --

If the fault persists, contact Huawei technical personnel.

----End

1.4 Troubleshooting Cases

This section presents several troubleshooting cases.

1.4.1 Can not Borrow an IP Address

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1.4.1 Can not Borrow an IP Address

Fault Symptom

The IP address of the Tunnel interface is ready to be obtained through IP address unnumbered.

The following shows the networking diagram.

Figure 1-6 Networking diagram of IP address unnumbered

SwitchB

SwitchA

Tunnel SwitchC

PC1

PC2

After the configuration, you find that Tunnel 9/0/1 cannot borrow the IP address of LoopBack0.

Fault Analysis

Check whether Tunnel 9/0/1 is configured with IP address unnumbered. Run the display this command in the interface view, and you can see the following information:

[S9300-A-Tunnel9/0/1] display this

# interface Tunnel9/0/1

tunnel-protocol mpls te

mpls te record-route label

mpls te route-pinning

mpls te lsp-tp outbound

As shown in the above information, Tunnel 9/0/1 in S9300-A is not configured with the IP address unnumbered.

Procedure

Step 1 Run the system-view command to enter the system view.

Step 2 Run the interface tunnel 9/0/1 command to enter the Tunnel interface view.

Step 3 Run the ip address unnumbered interface LoopBack 0 command to configure the IP address unnumbered.

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After the above configuration, you find that Tunnel 9/0/1 on Switch A can borrow the IP address from LoopBack 0.

----End

Summary

To configure IP address unnumbered, you need: l

Firstly ensure that the interface has configured with the IP address unnumbered.

Secondly ensure that the lending interface is correctly configured with an IP address.

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Troubleshooting - IP Service 2 DHCP Troubleshooting

DHCP Troubleshooting

About This Chapter

This chapter describes troubleshooting of DHCP, including the principle of DHCP, typical networking, troubleshooting procedure, troubleshooting cases.

2.1 Introduction to DHCP

This section describes the information that you need to know before troubleshooting DHCP.

2.2 Troubleshooting of the DHCP Server Based on the Global Address Pool

This section describes the notes about configuring the DHCP server, and provides the DHCP snooping troubleshooting flowchart and the troubleshooting procedure in a typical networking of the DHCP server based on the global address pool.

2.3 DHCP Relay Troubleshooting

This section describes the notes about configuring DHCP relay, and provides the DHCP relay troubleshooting flowchart and the troubleshooting procedure in a typical DHCP relay networking.

2.4 Troubleshooting Cases

This section presents the troubleshooting cases.

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2.1 Introduction to DHCP

This section describes the information that you need to know before troubleshooting DHCP.

With the rapid growth in network scales and complexity, for example, the location of hosts frequently changes (for portable computers or wireless networks) and the number of hosts exceeds the number of assignable IP addresses, network configurations become more difficult.

The Dynamic Host Configuration Protocol (DHCP) is developed to solve the preceding problems.

DHCP works in client/server model. The DHCP client requests the DHCP server for the configuration dynamically, and the DHCP server sends the configuration to the client dynamically.

2.1.1 DHCP Server

2.1.2 DHCP Relay

2.1.3 DHCP Proxy

2.1.4 Procedure for Obtaining the IP Address from the DHCP Server or the DHCP Relay Agent

2.1.5 DHCP Proxy Procedure

2.1.1 DHCP Server

The S9300 can function as the DHCP server to assign IP addresses to users. Generally, the DHCP server is used to assign IP addresses in the following scenarios: l l

On a large-scale network, it takes more time to manually assign IP addresses and it is difficult to manage the entire network

The number of hosts on the network is greater than that of the available IP addresses. Thus, not every host can be assigned a fixed IP address. A large number of clients need to dynamically obtain IP addresses through the DHCP server. In addition, the number of concurrent clients is limited.

Figure 2-1

shows a typical networking diagram of the DHCP server.

Figure 2-1 Typical networking diagram of the DHCP server

Switch

GE 1/0/1

Loopback0

10.10.10.100/32

DNS Server

1.1.1.1/24

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2.1.2 DHCP Relay

The early DHCP protocol applies to the situation where the DHCP client and DHCP server are located on the same network segment. Thus, it is necessary but uneconomical to configure a

DHCP server on each network segment to perform dynamic host configuration.

The DHCP relay function addresses the preceding problem. Through the DHCP relay function, clients can share DHCP servers on other network segments, and thus obtain valid IP addresses.

In this manner, DHCP clients on different network segments can use the same DHCP server.

This reduces costs and implements centralized management.

Figure 2-2

shows a typical networking diagram of DHCP relay.

Figure 2-2 Typical networking diagram of the DHCP relay agent

Internet

DHCP Server A

10.10.10.1/24

DHCP Server B

10.10.10.2/24

DHCP Relay

GE1/0/1

Switch

VLANIF100

20.20.20.1/24

DHCP

Client

DHCP

Client

VLAN100

DHCP

Client

2.1.3 DHCP Proxy

To manage DHCP users, the S9300 provides the DHCP proxy function. DHCP proxy manages users as follows: l l

DHCP proxy authenticates and authorizes access users with the local, remote (RADIUS or

HWTACACS), and non-authentication policies.

After the status of access users becomes normal, DHCP proxy is able to manage the specified user, for example, performs re-authentication, re-authorization, and accounting and forces users offline.

Figure 2-3

shows a typical networking diagram of DHCP proxy.

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Figure 2-3 Typical networking diagram of DHCP proxy

DHCP

Server

Multicast

Server

Quidway S9300 Terabit Routing Switch

Troubleshooting - IP Service

10.10.10.10

Router

Radius

Switch

GE 1/0/1.100

GE 1/0/2.100

LoopBack0

10.10.10.100/32

STB-A STB-B

2.1.4 Procedure for Obtaining the IP Address from the DHCP Server or the DHCP Relay Agent

Figure 2-4

shows the procedure for obtaining the IP address from the DHCP server or the DHCP relay agent.

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Figure 2-4 Procedure for obtaining the IP address from the DHCP server or the DHCP relay agent

DHCP messages

DHCP protocol stack

DHCP message parsing

DHCP Server DHCP Relay

AM module allocates

IP addresses

Send ACK messages

Select the DHCP server

Send Offer messages

Send messages

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The procedure for obtaining the IP address from the DHCP server is as follows:

The client broadcasts a DHCP DISCOVER packet and only DHCP servers replies to the packet.

After receiving the DHCP DISCOVER packet from the client, each DHCP server selects an unassigned IP address from the IP address pool, and then sends a DHCP OFFER packet with information about the leased IP address and other settings to the client.

If multiple DHCP servers send DHCP OFFER packets to the client, the client accepts the first received DHCP OFFER packet, and then broadcasts a DHCP REQUEST packet carrying information about the selected IP address.

After receiving the DHCP REQUEST packet, the DHCP server sends a DHCP ACK packet to the client. The DHCP ACK packet contains the offered IP address and other settings.

After the user obtains the IP address with the lease, the user access link is set up. Before the IP address lease expires, the user applies for extending the IP address lease. After being permitted by the local address pool or the DHCP server, the IP address lease of the user is extended. Otherwise, the user is forcibly disconnected from the network when the IP address expires. Then the user obtains the IP address according to the preceding procedure.

The procedure for obtaining the IP address from the DHCP relay agent is as follows:

After being initialized, the DHCP client broadcasts a configuration request packet, that is, a DHCP DISCOVER packet, on the local network. If there is no DHCP server on the local

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Troubleshooting - IP Service network, the device that is enabled with the DHCP relay function and is connected to the local network processes the received broadcast packet and forwards the packet to the corresponding DHCP server on another network.

The DHCP server configures the parameters contained in the received packet and sends the configuration to the DHCP client through the DHCP relay agent.

The DHCP client replies to the DHCP OFFER packet sent by the server by broadcasting a

DHCP REQUEST packet through the DHCP relay agent.The DHCP relay agent sends the

DHCP REQUEST packet in unicast mode to the DHCP server.

The DHCP server responds with a unicast DHCP ACK or DHCP NAK packet to the client through the DHCP relay agent.

2.1.5 DHCP Proxy Procedure

Figure 2-5

shows the DHCP proxy procedure.

Figure 2-5 DHCP proxy procedure

Client terminal

Discovery message

DHCPR

Create user

DHCPS UCM AAA AM

MAC Hush entry

Connection request

Create user entry

User authentication request

Offer message

CM connection response contains pool number

Forward Discovery

User authentication response

Apply address and gateway by pool number

Respond Offer

Allocate available address from address pool

Request message

Forward Request

ACK message

Respond ACK

Connection Up

Address renew or confirm request

Address application succeeds

User obtains

IP address

User goes online

2-6

The procedure for the DHCP proxy user to go online is as follows:

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After receiving DHCP Discovery or DHCP Request messages of the user, the DHCPR module sends connection setup requests to the UCM module.

The UCM module determines whether to permit the connection setup and allocate entries.

Then the UCM module notifies the AAA module for authentication. The AAA module performs local authentication or notifies the RADIUS module for remote authentication.

After AAA authentication ends, the AAA module notifies the UCM module of authentication results.

After receiving authentication response, the UCM module sends authentication connection setup information containing the address pool gateway and DHCP server to the DHCPR module.

The DHCPR module applies to the local or remote DHCP server for the IP address. After receiving the IP address allocated by the server, the DHCPR module notifies the UCM module that the connection is Up. Then the UCM module sends user entries through the

TM module.

After receiving the response of successfully sending entries, the UCM module notifies the

ARP module of performing online detection. The UCM module sends ACK messages about the connection being Up to the DHCPR module after receiving online detection response of the ARP module. The DHCPR module sends DHCP ACK messages to the user. Then the user goes online.

The UCM module notifies the AAA module of starting accounting. After receiving the remote accounting response, the AAA notifies the UCM module. After receiving the accounting response message of the AAA module, the UCM module processes the remaining duration or traffic in the response message and clears accounting failure counters if the accounting succeeds. The UCM module uses the policy for accounting start failures if the accounting fails.

2.2 Troubleshooting of the DHCP Server Based on the

Global Address Pool

2.2.1 Typical Networking

2.2.2 Configuration Notes

2.2.3 Troubleshooting Flowchart

2.2.4 Troubleshooting Procedure

2.2.1 Typical Networking

Figure 2-6

shows the typical networking of the DHCP server. Troubleshooting of the DHCP server based on the global address pool is based on this networking.

Figure 2-6

, the DHCP client and DHCP server are located on the same LAN and are connected through GigabitEthernet 1/0/1.

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Figure 2-6 Typical networking of the DHCP server

DHCP Clients DHCP Server

Quidway S9300 Terabit Routing Switch

Troubleshooting - IP Service

GE1/0/1

VLANIF100

DHCP Clients

2.2.2 Configuration Notes

Item

Configuring the global address pool

Subitem

Configuring an

IP address pool

Configuration Notes and Commands

The DHCP server assigns an IP address to a DHCP client by using an address pool.

To configure an IP address pool, run the following commands in sequence in the related views: dhcp enable

(system view)

dhcp select global (interface view)

ip pool ip-pool-name (system view)

To set the range of IP addresses in the IP address pool, run the network ip-address [ mask { mask | mask-length } ] command in the IP address pool view.

Setting the range of IP addresses in the

IP address pool

Setting the address lease

Different address pools can have different IP address leases on the DHCP server, whereas IP addresses in one address pool have the same lease. By default, the IP address lease is one day.

To set the address lease, run the lease { day day [ hour

hour [ minute minute ] ] | unlimited } command in the IP address pool view.

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Item

Configuring static binding between IP addresses and MAC addresses

Subitem

Binding an IP address to a

MAC address

Configuration Notes and Commands

When a user needs a fixed IP address, you can bind an idle

IP address in the IP address pool to the MAC address of the user. After the IP address is bound to the MAC address of the user, the lease of the IP address does not expire and the

IP address cannot be deleted when the user is using the IP address.

Before binding an IP address to a MAC address, you need to perform the task of Configuring the Egress Gateway of the DHCP Client.

To bind an IP address to a MAC address, run the static-

bind ip-address ip-address mac-address mac-address command in the IP address pool view.

2.2.3 Troubleshooting Flowchart

As shown in

Figure 2-6

, if a client cannot obtain an IP address after the global address pool is

configured, rectify the fault according to

Figure 2-7

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Figure 2-7 Troubleshooting flowchart of the DHCP server based on the global address pool

The client cannot acquire an IP address

Is the physical connection with the server in good shape

Yes

Enable the DHCP service

Ensure that the physical connection is in good shape

Is fault rectified

Yes

Is fault rectified

Yes

Is the global address pool configured

Yes

Configure the global address pool

Does the address in the address pool have the same network segment as the IP address of the interface

Modify either of the addresses to ensure that they are the same

Yes

Configure the client to acquire the IP address from the global address pool

Is fault rectified

Yes

Is fault rectified

Yes

Does the address pool have free addresses

Does the address pool have expired addresses

Does the address pool have conflicting addresses

Yes

Release conflicting addresses

Yes

Re-establish the global address pool

Is fault rectified

Yes

End

Seek technical support

Is fault rectified

Yes

Seek technical support

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2.2.4 Troubleshooting Procedure

Procedure

Step 1 Check that the physical connection is normal.

Set the IP address of the network adapter of the client connected to the DHCP server and ensure that the IP address of the network adapter of the DHCP client and the IP address of VLANIF

100 interface are located on the same network segment. Ping the IP address of VLANIF 100 interface from the DHCP client. If the ping operation succeeds, it indicates that the physical connection is normal.

You can also enable DHCP debugging on the server to check whether the server receives DHCP

Discover messages of the DHCP client.

Step 2 Check that the DHCP server is configured correctly.

The steps are as follows:

Run the dhcp enable command to enable DHCP.

Run the display ip pool all command to check whether a global address pool is created and whether the IP address in the global address pool and the IP address of VLANIF 100 interface are located on the same network segment.

If the global address pool is not created, run the ip pool ip-pool-name and network ip-

address [ mask { mask | mask-length } ] commands to create an IP address pool and set the range of IP addresses that can be dynamically allocated in the IP address pool. If the DHCP client cannot obtain an IP address, perform step c.

If the IP address pool is created, but IP addresses in the IP address pool and the IP address of VLANIF 100 interface are located on different network segments, modify either of them to ensure that both of them are located on the same network segment. If the DHCP client cannot obtain an IP address, perform step c.

If the IP address pool is created and IP addresses of the IP address pool and the IP address of VLANIF 100 interface are located on the same network segment, perform step c.

Run the dhcp select global command on VLANIF 100 interface to ensure that the DHCP client obtains an IP address from the global address pool. If the DHCP client cannot obtain an IP address, proceed to step 3.

Step 3 Check whether the global address pool has available IP addresses, expired IP addresses, or conflicting IP addresses.

The steps are as follows:

Run the display ip pool used command to check whether the global address pool has available IP addresses according to used IP addresses in the IP address pool. If yes, contact

Huawei technical personnel.

If not, run the display ip pool expired command to check whether the global address pool has expired IP addresses. If yes, contact Huawei technical personnel.

If not, run the display ip pool conflict command to check whether the global address pool has conflicting IP addresses.

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If not, it indicates that all the IP addresses in the address pool are used. In this case, you can create a global address pool containing the network segment of the previous one but with more IP addresses.

If yes, run the reset_ip_pool conflict command to release the conflicting IP addresses.

If the fault persists, contact Huawei technical personnel.

----End

2.3 DHCP Relay Troubleshooting

This section describes the notes about configuring DHCP relay, and provides the DHCP relay troubleshooting flowchart and the troubleshooting procedure in a typical DHCP relay networking.

2.3.1 Typical Networking

2.3.2 Configuration Notes

2.3.3 Troubleshooting Flowchart

2.3.4 Troubleshooting Procedure

2.3.1 Typical Networking

Figure 2-8

shows the typical networking of DHCP relay. DHCP relay troubleshooting is based

on this networking.

Figure 2-8 Typical networking of DHCP relay

DHCP Clients

GE1/0/1

VLANIF100

10.110.1.1/16

DHCP Relay

GE1/0/3

VLANIF101

20.110.1.1/16

GE1/0/2

VLANIF101

20.110.1.2/16

DHCP Server

2-12

Figure 2-8

: l l l

The DHCP client and the DHCP server are located on different LANs and are connected through the DHCP relay agent.

GigabitEthernet 1/0/1 of the DHCP relay agent is connected to the DHCP client. VLANIF

100 interface is enabled with the DHCP relay function and the DHCP server address is configured on VLANIF 100 interface.

GigabitEthernet 1/0/2 of the DHCP relay agent is connected to GigabitEthernet 1/0/3 of the DHCP server. Assume that the DHCP client is located on 10.110.0.0 and the DHCP

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Troubleshooting - IP Service 2 DHCP Troubleshooting server is located on 20.110.0.0. The DHCP server needs to allocate an IP address on

10.110.0.0 to the DHCP client through the DHCP relay agent.

2.3.2 Configuration Notes

Item

Configuring DHCP relay

Configuring the

DHCP server

Subitem

Enabling DHCP relay

Setting the DHCP server address on an interface enabled with DHCP relay

Configuring a global address pool

Configuration Notes and Commands

After DHCP relay is enabled, a VLANIF interface sends a DHCP message whose destination IP address is the local IP address to the external DHCP server. Then the external

DHCP server allocates an IP address to the

DHCP client.

To enable DHCP relay, run the following commands in sequence in the related views:

dhcp enable (system view)

dhcp select relay (interface view)

On the S9300, you can set the DHCP server address by using the following methods: l

Performing tasks of Configuring a DHCP

Server Group and Binding an Interface to a

DHCP Server Group l

Running the dhcp relay server-ip ip-

address command in the VLANIF interface view

When the DHCP relay agent is used to forward packets, the DHCP server must be configured with a global address pool.

To configure a global address pool, run the following commands in sequence in the related views: dhcp enable (system view)

dhcp select global (interface view)

ip pool ip-pool-name (system view)

2.3.3 Troubleshooting Flowchart

As shown in

Figure 2-8

, if a client cannot obtain an IP address through the DHCP relay agent,

rectify the fault according to

Figure 2-9

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Figure 2-9 Troubleshooting flowchart of DHCP relay

The client cannot acquire

an IP address

Quidway S9300 Terabit Routing Switch

Troubleshooting - IP Service

Is a correct route established between the relay and the server?

Yes

Does the relay have the address of the specified server?

Enable the DHCP

replay function

Configure the route

Set the address of the specified server on the replay

Diagnose and rectify the fault in the router according to the troubleshooting procedure for the DHCP server based on the global address pool

Is fault rectified?

Yes

Is fault rectified?

Yes

Is fault rectified?

Yes

Is fault rectified?

Seek technical support

Yes

End

2.3.4 Troubleshooting Procedure

Procedure

Step 1 Check that a reachable route exists between the DHCP relay agent and the DHCP server.

Assign 10.110.1.1 and 20.110.1.1 to VLANIF 100 interface and VLANIF 101 interface respectively, and then run the ping 20.110.1.1 command on the DHCP relay agent and run the

ping 10.110.1.1 command on the DHCP server to check whether the IP addresses can be pinged.

If the ping operation fails, run the display ip routing-table command on the DHCP relay agent and the DHCP server to check whether there are routing entries to each other.

If there are no routing entries to each other, run the ip route-static 0.0.0.0 0.0.0.0 20.110.1.1 and ip route-static 10.110.1.1 16 20.110.1.2 commands on the DHCP relay agent and the DHCP server to add static routes.

If the ping operation fails, check whether the physical connection is normal.

Step 2 Check the configurations of the DHCP relay agent.

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Check that the DHCP relay agent is configured with the DHCP server address, that is, the dhcp

relay server-ip 20.110.1.1 command is used on VLANIF 100 interface.

Run the display dhcp relay all command in the system view to check whether DHCP relay is enabled.

Step 3 Check the configurations of the DHCP server.

Run the display ip pool all command to check whether the global address pool is configured and view the range of IP addresses that are dynamically allocated.

Check whether the network segment where dynamically assigned IP addresses is located is the same as the network segment where the IP address of VLANIF 100 interface is located.

In this example, you need to check whether the network segment is configured as network

10.110.0.0 mask 255.255.0.0.

Step 4 Check that available IP addresses exist in the address pool.

Run the display ip pool used command to check whether the global address pool has available IP addresses according to used IP addresses in the IP address pool.

l l

If not, run the display ip pool expired command to check whether the global address pool has expired IP addresses.

If not, run the display ip pool conflict command to check whether the global address pool has conflicting IP addresses.

After the preceding steps, if there are no available IP addresses, expired IP addresses, or conflicted IP addresses in the address pool, it indicates that all IP addresses in the address pool are used. In this case, you can create an IP address pool containing the network segment of the previous one but with more addresses.

If there are available IP addresses in the address pool, and the configurations and physical links are normal, but the client cannot obtain an IP address, contact Huawei technical personnel.

----End

2.4 Troubleshooting Cases

This section presents the troubleshooting cases.

2.4.1 IP Address Assigned by the DHCP Server to a DHCP Client Conflicts with That of Another

DHCP Client

2.4.2 DHCP Client Cannot Obtain an IP Address from the DHCP Server

2.4.3 DHCP Client Cannot Obtain an IP Address Through the DHCP Relay Agent

2.4.1 IP Address Assigned by the DHCP Server to a DHCP Client

Conflicts with That of Another DHCP Client

Fault Symptom

After a client obtains an IP address from the DHCP server, information about IP address conflict is displayed when the client uses the IP address.

Figure 2-10

shows the networking.

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Figure 2-10 Conflict of the IP addresses obtained from the DHCP server

DHCP Clients DHCP Server

GE1/0/1

VLANIF100

DHCP Clients

Fault Analysis

A user on a network may set the IP address the same as the IP address allocated by the DHCP server to a host. As a result, IP addresses conflict.

Procedure

Step 1 Disable the network adapter of the client and ping the IP address of the DHCP client from another host to check whether the host with this IP address exists.

Step 2 If a response message is received, it indicates that the IP address has been statically configured by another user.

Step 3 Enable the network adapter of the client. In the Windows 98 operating system, run the

winipcfg command to release the IP address, and then apply for a new IP address. In the Windows

XP or Windows 2000 operating system or the DOS environment, run the ipconfig/release command to release the IP address, and then apply for a new IP address.

----End

Example

After the preceding configurations are completed, the DHCP client can successfully apply for an IP address, and the fault is thus rectified.

Summary

2-16

IP address conflict often occurs on a network. The cause is that another user on the network is configured with the same IP address.

If IP addresses conflict, run the ipconfig/release command on the client to release the IP address, and then run the ipconfig/renew command to apply for a new IP address. The DHCP server preferentially allocates the originally conflicting IP address. The conflicting IP address is added to the conflicting table when ICMP detects the conflict, and is not allocated in one hour. Then the DHCP server allocates a new IP address to the client.

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2.4.2 DHCP Client Cannot Obtain an IP Address from the DHCP

Server

Fault Symptom

As shown in

Figure 2-11

, after the global address pool is configured on the DHCP server, a

client cannot obtain an IP address.

Figure 2-11 Networking where a DHCP client cannot obtain an IP address from the DHCP server

DHCP Clients DHCP Server

GE1/0/1

VLANIF100

DHCP Clients

Fault Analysis

The possible causes are as follows: l l l

DHCP is disabled.

The global address pool and the IP address of GigabitEthernet 1/0/1 are located on different network segments.

The physical link is faulty.

Procedure

Step 1 Run the display ip pool all command. It is found that the global address pool is configured, with the network segment being 1.1.1.0 and the subnet mask being 255.255.0.0.

Step 2 Run the interface gigabitethernet 1/0/1 command in the system view to enter the view of

GigabitEthernet 1/0/1.

Step 3 Run the display this command. It is found that the IP address of GigabitEthernet 1/0/1 is 2.2.2.2.

That is, the IP address of GigabitEthernet 1/0/1 and the global address pool are located on different network segments.

Step 4 Run the ip address 1.1.1.1 16 command in the interface view to change the IP address of

GigabitEthernet 1/0/1 to 1.1.0.0. You can also change the network segment in the global address pool to be the network segment where the IP address of GigabitEthernet 1/0/1 is located.

----End

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Example

After the preceding configurations are completed, the DHCP client can successfully apply for an IP address, and the fault is thus rectified.

Summary

On a network where a client is directly connected to the DHCP server, when the global address pool is used for IP address allocation, the global address pool and the IP address of

GigabitEthernet 1/0/1 must be located on the same network segment.

2.4.3 DHCP Client Cannot Obtain an IP Address Through the

DHCP Relay Agent

Fault Symptom

As shown in

Figure 2-12

, the DHCP client cannot obtain an IP address through the DHCP relay

agent.

Figure 2-12 Networking where a DHCP client cannot obtain an IP address through the DHCP relay agent

DHCP Clients

GE1/0/1

VLANIF100

10.110.1.1/16

DHCP Relay

GE1/0/3

VLANIF101

20.110.1.1/16

GE1/0/2

VLANIF101

20.110.1.2/16

DHCP Server

Fault Analysis

Run the display ip pool all command to check that the DHCP server is configured with an address pool on the network segment where the DHCP client resides.

Run the display ip interface brief command to view the configuration of the DHCP relay agent and the DHCP server. Then you can check whether each interface is configured with the correct IP address.

Run the display dhcp relay all command to check that the interface enabled with the DHCP replay function is configured with the DHCP server address.

On the DHCP relay agent, run the ping 20.110.1.1 command. You can find that the ping operation succeeds. On the DHCP server, run the ping 10.110.1.1 command. You can find that the ping operation succeeds. This indicates that the route is correct.

Check the networking to check whether more than four DHCP relay agents are configured.

In the troubleshooting case, the number of DHCP relay agents is within the limit.

Run the debugging dhcp server packet command to enable DHCP debugging on the

DHCP server. Then you can find that the DHCP server does not receive any DHCP Discover

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Procedure

Step 1 Check that the DHCP server is configured with an address pool on the network segment where the DHCP client resides.

Step 2 Check that the interface on the DHCP relay agent that is connected to the DHCP client is configured with the corresponding DHCP server address. Check that no IP address conflict occurs because multiple corresponding DHCP server addresses are configured.

Step 3 Check that the DHCP relay function is enabled.

Step 4 Check that the DHCP relay agent and the DHCP server are configured with reachable routes.

Step 5 Check the DHCP configurations to check that less than four DHCP relay agents are configured.

Step 6 Check whether the interface is enabled with the DHCP relay function. If not, run the dhcp select

relay command in the view of GigabitEthernet 1/0/1.

----End

Example

message from the DHCP client. Run the debugging dhcp relay packet command to enable

DHCP debugging on the DHCP relay agent. Then you can find that the DHCP relay agent receives the DHCP Discover message from the DHCP client. It is inferred that the DHCP relay agent does not forward the DHCP Discover message.

Check the configurations of the DHCP relay agent, and you can find that the dhcp select

relay command is not used. As a result, the DHCP relay function does not take effect.

After the preceding configurations are completed, the DHCP client can successfully apply for an IP address, and the fault is thus rectified.

Summary

When a DHCP client applies to the DHCP server for an IP address through the DHCP relay agent, the DHCP server must be configured with the IP address pool on the network segment where the IP address of the DHCP client is located. In addition, the IP address of the interface enabled with the DHCP relay function must be located on the network segment where the IP address of the DHCP client is located.

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Troubleshooting - IP Service 3 DHCPv6 Troubleshooting

DHCPv6 Troubleshooting

About This Chapter

This section describes the DHCPv6 troubleshooting flowchart and the troubleshooting procedure in a typical DHCP relay networking and presents troubleshooting cases.

3.1 DHCPv6 Relay Troubleshooting

This section describes the notes about configuring DHCPv6 relay, and provides the DHCPv6 relay troubleshooting flowchart and the troubleshooting procedure in a typical DHCPv6 relay networking.

3.2 Troubleshooting Cases

This section presents a troubleshooting case of DHCPv6.

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3.1 DHCPv6 Relay Troubleshooting

This section describes the notes about configuring DHCPv6 relay, and provides the DHCPv6 relay troubleshooting flowchart and the troubleshooting procedure in a typical DHCPv6 relay networking.

3.1.1 Troubleshooting Flowchart

3.1.2 Troubleshooting Procedure

3.1.1 Troubleshooting Flowchart

Clients cannot obtain IPv6 addresses through the DHCPv6 relay agent. To rectify the fault,

follow the troubleshooting flowchart shown in

Figure 3-1

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Figure 3-1 DHCPv6 relay troubleshooting flowchart

Clients cannot obtain

IPv6 addresses through DHCPv6 relay

Is user interface added to correct

VLAN?

Yes

DHCP enabled globally?

Yes

Is there IPv6 license?

Yes

Is IPv6 enabled globally?

Yes

Is IPv6 enabled on an interface?

Yes

Is DHCPv6 relay enabled on an interface?

Yes

Can device and server be pinged?

Yes

Is fault rectified?

Add user interface to correct VLAN

Enable DHCP

Apply for the

IPv6 license

Enable IPv6

Enable IPv6 on an interface

Enable DHCP relay on an interface

Troubleshoot link problem

Yes

End

Seek technical support

3 DHCPv6 Troubleshooting

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3.1.2 Troubleshooting Procedure

Procedure

Step 1 Check that the user interface is added to a specified VLAN.

If the user interface is not added to a specified VLAN, user packets may be forwarded incorrectly or discarded. If user packets are not forwarded to the DHCP server, users cannot obtain IPv6 addresses.

Step 2 Check whether DHCP is enabled globally.

[Quidway] display this

dhcp enable

Return

If DHCP is not enabled globally, the Switch does not process DHCPv6 messages sent by users.

Step 3 Run the display license command to check whether there is the IPv6 license. The IPv6 function of the Switch is controlled by the license.

NOTE

Generally, the IPv6 commands can be run on a new device, but the corresponding IPv6 functions cannot take effect. To make the IPv6 functions effective on the Switch, contact local office of Huawei to buy the license.

Step 4 Check whether IPv6 is enabled. If IPv6 is not enabled, the Switch does not forward IPv6 packets.

[Quidway] display this

ipv6

Return

Step 5 Check whether IPv6 is enabled on the VLANIF interface. If IPv6 is not enabled on the VLANIF interface, the IPv6 address cannot be set on the VLANIF interface.

Step 6 Check whether DHCPv6 relay is enabled on the VLANIF interface. If DHCPv6 relay is not enabled on the VLANIF interface, DHCPv6 users cannot obtain IPv6 addresses in another network segment.

Method 1: Run the display this command on the VLANIF interface connected to the client to check whether the dhcpv6 relay destination command is used on the VLANIF interface.

[Quidway-Vlanif10] display this

# interface Vlanif10

ipv6 enable

ipv6 address 1:2::3:4/36

dhcpv6 relay destination 2:1::3:2

Return

Method 2: Run the display dhcpv6 relay command in the system view on the Switch to check whether the configuration of the interface enabled with DHCPv6 relay is correct.

[Quidway] display dhcpv6 relay

Interface Mode Destination

Vlanif10 Relay 2:1::3:2

Run the dhcpv6 relay destination command to enable DHCPv6 relay on the VLANIF interface and set the IPv6 address of the DHCPv6 server or next-hop relay agent. Before running the

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dhcpv6 relay destination command, you must enable DHCP globally. Otherwise, the configuration cannot be performed.

If the configuration fails, check whether the interface is configured with eight destination addresses. On the Switch, up to eight interfaces can be enabled with DHCPv6 relay and each interface can be configured with up to eight destination addresses.

If the configured IPv6 address is a global address or a site address, the outbound interface does not need to be specified. The DHCPv6 server sends relay messages to the IPv6 address by searching for a route. If the configured IPv6 address is a local address or a multicast address, the outbound interface of the DHCPv6 server needs to be specified.

Step 7 Check that the user gateway and the DHCPv6 server can ping each other.

Ping the DHCPv6 server from the IPv6 address of the VLANIF interface enabled with DHCP relay. If the ping operation fails, it indicates that the physical link between the Switch and the DHCPv6 server is faulty. In this case, the DHCPv6 server cannot allocate addresses to users on the Switch.

Ping the IPv6 address of the VLANIF interface enabled with DHCP relay from the DHCPv6 server. If the ping operation fails, it indicates that the physical link between the Switch and the DHCPv6 server is faulty. In this case, the DHCPv6 server cannot allocate addresses to users on the Switch.

Check whether physical links between the DHCPv6 client and the DHCPv6 relay agent and between the DHCPv6 relay agent and the DHCPv6 server are faulty and locate faults.

If the fault persists, contact Huawei technical personnel.

----End

3.2 Troubleshooting Cases

This section presents a troubleshooting case of DHCPv6.

3.2.1 Clients Cannot Obtain IPv6 Addresses Through DHCPv6 Relay

3.2.1 Clients Cannot Obtain IPv6 Addresses Through DHCPv6

Relay

Fault Symptom

As shown in

Figure 3-2

, the Switch functions as the DHCPv6 relay agent. It is found that clients cannot obtain IPv6 addresses.

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Figure 3-2 Networking where clients cannot obtain IPv6 addresses

DHCPv6 client DHCPv6 client

GE1/0/1

VLANIF10

2000::1/64

Switch

GE1/0/2

VLANIF20

3000::1/64

DHCPv6 relay agent

3000::3/64

DHCPv6 server

DHCPv6 client DHCPv6 client

Fault Analysis

The possible causes are as follows: l l l

VLANIF 10 is not enabled with DHCPv6 relay.

IPv6 addresses of VLANIF 20 and the DHCPv6 server interface address are in different network segments.

The physical link is faulty.

Procedure

Step 1 Check whether GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 are added to a correct VLAN.

Run the display this command on GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 to check whether GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 are added to a correct VLAN.

[Quidway-GigabitEthernet1/0/1] display this

# interface gigabitethernet 1/0/1

port hybrid pvid vlan 10

port hybrid untagged vlan 10

Return

[Quidway-GigabitEthernet1/0/2] display this

# interface gigabitethernet 1/0/2

port hybrid pvid vlan 20

port hybrid untagged vlan 20

Return

Step 2 Check whether DHCP and IPv6 are enabled globally.

[Quidway] display this

dhcp enable

ipv6

Return

Step 3 Check whether VLANIF 10 is enabled with DHCPv6 relay.

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Example

Run the display this command on VLANIF 10 to check whether the dhcpv6 relay

destination command is used on VLANIF 10.

[Quidway-Vlanif10] display this

# interface Vlanif10

ipv6 enable

ipv6 address 2000::1/64

dhcpv6 relay destination 3000::3/64

Return

Step 4 Check whether the IPv6 address of VLANIF 20 is correctly set.

Run the display this command on VLANIF 20 to check whether IPv6 addresses of VLANIF 20 and the DHCPv server interface are in the same network segment.

[Quidway-Vlanif20] display this

# interface Vlanif20

ipv6 enable

ipv6 address 3001::1/64

Return

According to the preceding output, the IPv6 address of VLANIF 20 is 3001::1/64, whereas the

IPv6 address of the DHCPv6 server interface is 3000::3/64. That is, IPv6 addresses of VLANIF

20 and the DHCPv server interface are in different network segments.

Change the IPv6 address of VLANIF 20 to 3000::1/64.

[Quidway-Vlanif20] ipv6 address 3000::1 64

----End

After the preceding configuration, DHCP clients can obtain IPv6 addresses, and the fault is thus rectified.

Summary

Ensure that IPv6 addresses of the VLANIF interface connecting the DHCPv6 relay agent and the DHCPv6 server and the DHCPv6 server interface are in the same network segment.

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Troubleshooting - IP Service 4 UDP Helper Troubleshooting

UDP Helper Troubleshooting

About This Chapter

This chapter describes troubleshooting of the User Datagram protocol (UDP) helper, including the principle of UDP helper, typical networking, troubleshooting procedure, troubleshooting cases, FAQs, and diagnostic tools.

4.1 UDP Helper Overview

This section describes the information that you need to know before troubleshooting the UDP helper.

4.2 UDP Helper Troubleshooting

This section describes the notes about configuring the UDP helper, and provides the UDP helper troubleshooting flowchart and the troubleshooting procedure in typical UDP helper networking.

4.3 Troubleshooting Cases

This section presents several troubleshooting cases.

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4.1 UDP Helper Overview

This section describes the information that you need to know before troubleshooting the UDP helper.

A UDP helper functions as a relay to forward the broadcast UDP packets with specified destination port numbers. It converts the broadcast UDP packets to unicast UDP packets and sends them to the specified server. The UDP helper can forward broadcast packets from a subnet to another subnet.

4.2 UDP Helper Troubleshooting

This section describes the notes about configuring the UDP helper, and provides the UDP helper troubleshooting flowchart and the troubleshooting procedure in typical UDP helper networking.

4.2.1 Typical Networking

4.2.2 Configuration Notes

4.2.3 Troubleshooting Flowchart

4.2.4 Troubleshooting Procedure

4.2.1 Typical Networking

Figure 4-1

shows the typical networking diagram of a UDP helper. Troubleshooting of the UDP helper is based on the networking.

Figure 4-1 Typical networking diagram of the UDP helper

VLANIF2

VLANIF1

1.1.1.1/24

VLANIF2

2.2.2.1/24 Switch

VLANIF3

3.3.3.1/24

Internet

Switch

Server

1.1.1.10/32

4-2

User2

2.2.2.10/32

User3

2.2.2.11/32

User1

3.3.3.10/32

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As shown in

Figure 4-1

User 2 and User 3 belong to the same VLAN 2.

User 1 belongs to the VLAN 3.

The server belongs to the VLAN 1.

User 1 periodically sends broadcast packets such as NETBIOS-NS packets to query information about datagrams on the network.To query information about datagrams of a device in a different

VLAN, for example, Server, User 1 requires a UDP helper to forward the query packets to Server.

4.2.2 Configuration Notes

Item

Setting port numbers for the

UDP helper

Sub-item

Enabling the

UDP helper

Setting port numbers for the UDP helper

Configuration Notes and Commands

After the UDP helper is enabled, the UDP helper takes effect for the following UDP destination port numbers by default: l

DNS: domain name service (53) l

NETBIOS-DS: NETBIOS datagram service (138) l

NETBIOS-NS: NETBIOS name service (137) l

TACAS: Terminal Access Controller Access-Control System

(49) l

TFTP: Trivial File Transfer Protocol (69) l

Time Service: 37

When the UDP helper is disabled, all the configured UDP port numbers are deleted.

To enable the UDP helper, run the udp-helper enable command in the system view. To disable the UDP helper, run the undo

udp-helper enable command in the system view.

The UDP helper cannot be used to relay DHCP packets. That is, the destination port number cannot be set to 67 or 68.

You can set up to 40 UDP port numbers on the S9300.

To set a UDP port number, run the udp-helper port port-

number command in the system view. To delete a UDP port number, run the undo udp-helper port port-number command in the system view.

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Item

Configur ing the

UDP helper server

Sub-item

Configuring the UDP helper server

Configuration Notes and Commands

You can configure up to 20 destination servers to which the packets can be relayed on a VLANIF interface.

When specifying the IP address of a destination server, ensure that the S9300 has a reachable route to the server; otherwise, packet relay fails.

A UDP port number takes effect globally. That is, if a UDP port number is set, all the VLANIF interfaces configured with destination servers forward the packets with this port number.

You cannot configure a single VLANIF interface to forward packets with the specified UDP port number.

To configure a UDP helper server, run the udp-helper server

ip-address command in the VLANIF interface view. To delete a UDP helper server, run the undo udp-helper server ip-

address command in the VLANIF interface view.

4.2.3 Troubleshooting Flowchart

Figure 4-2

shows the flowchart of UDP helper troubleshooting.

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Figure 4-2 UDP helper troubleshooting flowchart

UDP helper is unavailble

4 UDP Helper Troubleshooting

Is UDP helper enabled?

Yes

Enable UDP helper

Is the fault rectified?

Yes

Is UDP port number set?

Yes

Set the UDP port number

Is the fault rectified?

Yes

End

Is destination server specified?

Yes

Specify the destination server

Check the route between the local device and the server

Is the fault rectified?

Yes

Is the fault rectified?

Yes

End

Seek technical support

End

4.2.4 Troubleshooting Procedure

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Procedure

Step 1 Check and ensure that the UDP helper is enabled.

Run the display this command in the system view to check whether the UDP helper is enabled.

If the UDP helper is not enabled, run the udp-helper enable command to enable it. If the

UDP helper is enabled, proceed to

Step 2

Step 2 Check and ensure that the UDP port numbers are set correctly.

Run the display this command in the system view to check the UDP port numbers.

After the UDP helper is enabled, the S9300 relays the broadcast packets whose destination port numbers are 37, 49, 53, 69, 137, and 138 by default.

If the corresponding UDP port numbers are set, proceed to

Step 3

Step 3 Check and ensure that the destination server is configured.

Run the display this command in the VLANIF interface to view the configuration of the destination server.

If the destination server is configured correctly, proceed to

Step 4

Step 4 Check the route between the S9300 and the destination server.

Run the display ip routing-table command to check whether the routing table contains the route to the destination server.

If the route exists but the fault persists, contact Huawei technical personnel.

----End

4.3 Troubleshooting Cases

This section presents several troubleshooting cases.

4.3.1 UDP Packets Cannot Be Relayed to the Destination Server

Fault Symptom

On the network as shown in

Figure 4-3

, the UDP helper is enabled, but the function does not take effect.

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Figure 4-3 Networking diagram of the UDP helper

VLANIF2

VLANIF1

1.1.1.1/24

VLANIF2

2.2.2.1/24 Switch

VLANIF3

3.3.3.1/24

Switch

Internet

4 UDP Helper Troubleshooting

Server

1.1.1.10/32

User2

2.2.2.10/32

User3

2.2.2.11/32

User1

3.3.3.10/32

Fault Analysis

Possible causes are as follows: l l l l

The UDP helper is not enabled.

The UDP port number is not set.

The destination server is not configured.

The route between the S9300 and the destination server is unreachable.

Procedure

l Locating the fault

Run the display this command in the system view to check whether the UDP helper is enabled.

If the UDP helper is disabled, run the udp-helper enable command to enable it.

Run the display this command in the system view to check whether the UDP port number is set.

If the UDP port number is not set, run the udp-helper port port-number command to set the port number.

Run the display this command in the VLANIF interface view, and you can find that the IP address of the destination server is 1.1.1.11. The S9300 does not have a route to the destination server; therefore, the UDP helper function is unavailable.

l Rectifying the fault

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Run the system-view command to enter the system view.

Run the interface vlanif 3 command to enter the VLANIF interface view.

Run the udp-helper server 1.1.1.10 command to configure the destination server.

Run the return command to return to the user view.

Run the save command to save the configuration.

----End

Summary

When configuring the UDP helper, ensure that the configuration of the destination server is correct; otherwise, the UDP helper function is unavailable.

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