4 UDP Helper Troubleshooting
Quidway S9300 Terabit Routing Switch
Troubleshooting - IP Service
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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Quidway S9300 Terabit Routing Switch
Troubleshooting - IP Service 4 UDP Helper Troubleshooting
As shown in
Figure 4-1
:
l
User 2 and User 3 belong to the same VLAN 2.
l
User 1 belongs to the VLAN 3.
l
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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Troubleshooting - IP Service
Figure 4-2 UDP helper troubleshooting flowchart
UDP helper is unavailble
4 UDP Helper Troubleshooting
Is UDP helper enabled?
Yes
No
Enable UDP helper
No
Is the fault rectified?
Yes
Is UDP port number set?
Yes
No
No
Set the UDP port number
Is the fault rectified?
Yes
End
End
Is destination server specified?
Yes
No
Specify the destination server
Check the route between the local device and the server
Is the fault rectified?
No
Yes
Is the fault rectified?
Yes
End
No
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.
1.
Run the display this command in the system view to check whether the UDP helper is enabled.
2.
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.
1.
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.
2.
If the corresponding UDP port numbers are set, proceed to
Step 3
.
Step 3 Check and ensure that the destination server is configured.
1.
Run the display this command in the VLANIF interface to view the configuration of the destination server.
2.
If the destination server is configured correctly, proceed to
Step 4
.
Step 4 Check the route between the S9300 and the destination server.
1.
Run the display ip routing-table command to check whether the routing table contains the route to the destination server.
2.
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
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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Troubleshooting - IP Service
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
1.
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.
2.
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.
3.
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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Troubleshooting - IP Service
1.
Run the system-view command to enter the system view.
2.
Run the interface vlanif 3 command to enter the VLANIF interface view.
3.
Run the udp-helper server 1.1.1.10 command to configure the destination server.
4.
Run the return command to return to the user view.
5.
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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