Switch configuration - Systems & Network Training

Switch configuration
By the end of this session, you will be able to:
•
Describe basic switch configuration methods.
•
Configure a switch.
4
SESSION OVERVIEW ...................................................... 2
MANAGEMENT OPTIONS ............................................... 3
WHY CONFIGURE SWITCHES? ....................................... 4
CONSOLE PORT ............................................................. 5
HYPERTERMINAL ......................................................... 6
TROUBLESHOOTING...................................................... 7
QUIZ ............................................................................. 8
EXERCISE ..................................................................... 9
Switch configuration
Chapter 4: Switch configuration
Systems & Network Training
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-2
Switch configuration
5 ways to manage switches
Console
Console port
Network ports
telnet
SNMP
HTTP
TFTP
Systems & Network Training
Management options
•
After the hardware has been installed and cabled it is likely that at least a minimal
additional configuration would be required.
•
Until an IP address has been assigned configuration is performed using the console
port (usually at the rear of the switch).
•
Most switch management options require network access and a valid IP address for
the switch.
•
If and when the switch has a network connection and a valid IP address, then a
number of options for switch management are possible:
telnet
Accesses the command line – similar to console port access but over
the network.
SNMP (Simple Network Management Protocol)
For management using network management systems such as HP
OpenView.
HTTP (Hyper Text Transfer Protocol)
Web based management. The switch acts as a web server, the
administrator just points the browser at the switch.
TFTP (Trivial File Transfer Protocol)
Used to download configurations.
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-3
Switch configuration
Why configure switches?
Console
Console port
1. Passwords
2. Management
3. Performance
SNMP
telnet
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Why configure switches?
•
Switches are layer 2 devices and are therefore relatively easy to configure in
comparison to routers.
•
In most cases, the default configuration of switches will enable the switch to connect
PCs and servers together with ease - plug and play.
•
Further configuration of switches is advisable for the following reasons:
Security
Adding passwords to the switch to prevent unauthorised access.
Management
An IP address is advisable to enable management of the switch and
should be configured.
Performance
With an “out of the box” configuration, convergence times of 50+
seconds would not be uncommon. With a little bit of effort these times
can be reduced to 0-8 seconds. Extra configuration can also make the
network more stable and less prone to issues, such as broadcast storms.
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-4
Switch configuration
Console port
Console port
Cisco 2900
Extreme Summit24
Foundry BigIron
4000
3 3Com
com 3300
3300
Systems & Network Training
Console port
•
The normal place to start configuring is via a console port.
•
This is the only option if the switch does not have an IP address configured.
•
The console cable is connected directly to the switch.
•
The console connector is normally in the back of the switch, as shown above.
•
The console connector is normally a 9-pin D type serial connector.
•
However, Cisco uses an RJ connector, furthermore with a special “roll over cable”.
•
The other end of the console cable will be connected to a dumb ASCII terminal or the
COM port of a PC.
•
Note that some switches do not provide a console port.
•
In this case a default IP address is usually provided.
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-5
Switch configuration
HyperTerminal
COM port
(not modem)
Speed
Flow control
Systems & Network Training
HyperTerminal
•
HyperTerminal is the usual software to use when connecting your PC to the console
port on a switch.
•
The main reason for using HyperTerminal is that it is free and comes with Microsoft
Windows.
•
The settings for HyperTerminal need to match the console port settings on the switch.
•
A typical configuration is:
Speed:
Data bits:
Parity:
Stop bits:
Flow control:
•
9600
8
None
1
None
When using HyperTerminal, your PC is effectively acting as a screen and keyboard
for the switch.
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-6
Switch configuration
Basic troubleshooting
LEDs
Do not underestimate
their usefulness in troubleshooting
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Troubleshooting
•
For troubleshooting the following is also available:
LEDs
IP not required.
On connection of a cable the port LED should change
colour (as long as the connected device is active). If the
LED remains off after connection this is an indication
that either the connected device is off or that the wrong
cable type is being used.
Analyser ports
IP not required.
By their nature switches do not allow analysers to work
as the switches filter traffic. Most switches allow a port
to be configured as an “analyser” port which stops
filtering on that port. This then allows an analyser
attached to that port to see all packets.
Beware of legal issues of snooping if carrying other
peoples’ traffic.
Log files
IP not required.
Most network devices provide log files, which provide a
record of the messages that have been displayed on the
screen. Syslog can often be used to allow these log files
to be stored on a remote machine (syslog requires IP).
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-7
Switch configuration
Quiz
1.
Name and describe five ways of configuring a switch.
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_______________________________________
_______________________________________
_______________________________________
_______________________________________
2.
Name three reasons for configuring a switch.
_______________________________________
_______________________________________
_______________________________________
3.
What is HyperTerminal used for?
_______________________________________
4.
Why isn't telnet used for initial configuration?
_______________________________________
5.
If the LED on a port is not lit what is probably wrong?
_______________________________________
6.
When connecting a PC to a switch which type of cable should be used?
Straight through or cross over?
_______________________________________
7.
When connecting a switch to a switch which type of cable should be used?
Straight through or cross over?
_______________________________________
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-8
Switch configuration
Exercise: Hub based network
Hub
10.1.1.1
10.2.1.1
10.3.1.1
10.4.1.1
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Exercise
Building a hub based network
The main purpose of this stage of the exercise is to provide a contrast to when we use a
switch (instead of the hub). Key points to discover in the exercise are:
Hubs need no configuration to work.
Traffic sent to one PC is actually sent everywhere.
1.
Connect your PC to a hub as shown above. What cable type is used?
_______________________________________
2.
Although this is a layer 2 Ethernet switching course, networks always use higher
layers as well. We will use ping as a test tool. To use ping we first need to set IP
addresses on the PCs. Record your IP address here.
_______________________________________
We will use subnet masks of 255.0.0.0
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-9
Switch configuration
To set your IP address under XP:
Right click on My network places.
Left click properties.
Right click local area connection.
Left click properties.
Highlight TCP/IP.
Click the properties button.
Select use the following IP address.
Fill in the IP address and subnet mask.
Click OK and then close.
3.
Open a command prompt on your PC. (For example using Start --> Run, cmd)
Now type:
ipconfig /all
What is the MAC address of your PC?
_______________________________________
4.
Set up Ethereal (a LAN analyser) and start capturing packets. From your command
prompt, ping the IP address of another PC. Now stop the packet capture and answer
the following questions:
What is the source MAC address of your echo requests?
_______________________________________
Are pings between other PCs also seen? (If not try capturing packets again whilst two
other PCs are pinging.)
_______________________________________
What is the average time for a ping? Use either the ping output or the packet
captures to answer this question.
_______________________________________
5.
Can you ping the hub? Why not?
_______________________________________
_______________________________________
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-10
Switch configuration
Exercise: Switch based network
Hub
10.1.1.1
10.2.1.1
10.3.1.1
10.4.1.1
Systems & Network Training
Building a switch based network
In this part of the exercise the hub is replaced with a switch. Key points to discover in the
exercise are:
Switches need no configuration to work.
Switches do not need an IP address to do their job of switching.
Traffic is only sent to the ports that need the traffic.
6.
The switches are 10/100 auto sensing. What does this mean?
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7.
Move your PC from the hub and connect it to the switch.
8.
How would you know if you have connectivity?
_______________________________________
9.
If you do not have connectivity check the following:
Switch/PC powered on?
_______________________________________
Correct cables used?
_______________________________________
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-11
Switch configuration
10.
Use Ethereal and start capturing packets. From your command prompt, ping the IP
address of another PC. Now stop the packet capture and answer the following
questions:
Are pings between other PCs also seen? (If not try capturing packets again whilst two
other PCs are pinging). If still not, why not?
_______________________________________
_______________________________________
What is the average time for a ping? Use either the ping output or the packet
captures to answer this question. Is the switch faster than the hub?
_______________________________________
_______________________________________
11.
Can you ping the switch? Why not?
_______________________________________
_______________________________________
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-12
Switch configuration
Exercise: Configuring the switch
Console
Network port
Systems & Network Training
Configuring switches
In this part of the exercise each student will now use, and configure, his or her own switch.
Key points to discover in this part of the exercise are:
How to use HyperTerminal and console port access.
Theoretical knowledge such as bridge tables, covered earlier in the course, is
not just theory – bridge tables are real and can be seen.
Reading the output of commands is an essential part of the job.
Note: The switches that we are using happen to be Cisco switches (they have a large market
share). However, this is not a Cisco course. If you have any problems whatsoever with the
command line please ask the instructor straight away – the main emphasis of the exercise is
on switches in general, not a specific manufacturer’s switch.
Please use the quick reference at the back if you wish.
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-13
Switch configuration
The main points for Cisco switches are:
•
To configure the Cisco from scratch connect to the router using a rollover cable and
connect into the console port of the router from the PCs COM port.
•
Use HyperTerminal with 9600 and no flow control to “drive” the Cisco.
•
To do anything useful you must be in privileged mode.
•
To enter privileged mode type:
enable
•
In privileged mode the main commands are:
?
show
configure t
On line help
To look at something
Enter configuration mode.
•
Configuration mode allows changing the configuration.
•
To save the configuration
copy run start
•
Once again, any problems with the user interface please ask the Instructor.
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-14
Switch configuration
12.
Connect your PC to the console port of the switch. What software needs to be used for
this?
_______________________________________
13.
Reboot the switch and text similar to the following should appear. The switch is
asking whether you want to set up the switch. At this stage we will say no.
00:00:27: %SYS-5-RESTART: System restarted -Cisco Internetwork Operating System Software
IOS (tm) C2900XL Software (C2900XL-C3H2S-M), Version
12.0(5)XU, RELEASE SOFTWARE
(fc1)
Copyright (c) 1986-2000 by cisco Systems, Inc.
Compiled Mon 03-Apr-00 16:37 by swati
--- System Configuration Dialog --At any point you may enter a question mark '?' for help.
Use ctrl-c to abort configuration dialog at any prompt.
Default settings are in square brackets '[]'.
Continue with configuration dialog? [yes/no]:
If you do not get the above output, check the following items:
Correct console cable and connector used?
Check by swapping with known good parts.
Switch powered on?
Check power LED on switch.
HyperTerminal settings correct?
9600, no flow control, rest defaults.
Correct COM port used?
COM1 or COM2?
You should be faced with the user mode prompt after you typed no.
14.
At this stage type
enable
to enter privileged mode. No password should be asked for, as we have not yet setup
the switch. Your prompt should now look something like:
Switch#
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-15
Switch configuration
Now type
sh mac
which will display the “bridge” table. The output should look something like this:
Switch# sh mac
Dynamic Address Count:
1
Secure Address Count:
0
Static Address (User-defined) Count:
0
System Self Address Count:
47
Total MAC addresses:
48
Maximum MAC addresses:
2048
Non-static Address Table:
Destination Address Address Type VLAN Destination Port
------------------- ------------ ---- ---------------00e0.9806.d9b2
Dynamic
1 FastEthernet0/9
15.
Looking at the output above AND on your screen answer each of the following
questions twice. Once for the real screen output and once for the output above.
How many machines are connected to the switch?
__________________
__________________
How many MAC addresses does this switch have itself?
__________________
__________________
On what port is (are) the PC(s) attached?
__________________
__________________
How has the switch learnt that address?
__________________
__________________
What is the maximum size of the bridge table? How will this affect the performance
of the switch?
__________________ __________________
_______________________________________
16.
Now look at one of the interfaces with a PC attached. To do this:
switch# show interface fa 0/9
where 0/9 is the port number with the PC attached.
The output should look something like that shown over.
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-16
Switch configuration
Switch# sh int fa 0/9
FastEthernet0/9 is up, line protocol is up
Hardware is Fast Ethernet, address is 0002.4b88.4689 (bia
0002.4b88.4689)
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive not set
Auto-duplex (Half), Auto Speed (10), 100BaseTX/FX
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 00:00:01, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
8 packets input, 512 bytes
Received 7 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast
0 input packets with dribble condition detected
579 packets output, 22456 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
17.
Looking at the output above AND on your screen answer each of the following
questions twice. Once for the real switch and once for the output above.
Which duplex is in use?
__________________
__________________
__________________
__________________
__________________
__________________
__________________
__________________
How many broadcasts have there been?
__________________
__________________
What does bia stand for?
Is the port being used?
What speed is the port being used at?
How many collisions?
__________________
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
__________________
4-17
Switch configuration
18.
Type the following
show ip int brief
At this stage we are not worried about the IP addressing but how many ports are in
use?
_______________________________________
19.
So far we have used the switch and looked at items discussed in the theory sessions.
We will now configure the switch in a simple fashion by shutting down (disabling) a
port. Type the following:
conf t
This enters configuration mode. Note the prompt has changed.
int fa0/9
where 0/9 is the name of the port you wish to disable.
shut
This command disables the port.
exit
exit
We are now back in privileged mode where we can look at
things.
20.
What has happened to the LED for the port shut down?
_______________________________________
21.
Now repeat the show ip interface brief command. Before the output would
have shown the interface as being “up up”. What state is the port now in?
_______________________________________
22.
Re-enable the port which was shut down:
conf t
int fa0/9
no shut
exit
exit
23.
What does this do to the show ip interface brief output and the LEDs?
_______________________________________
_______________________________________
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-18
Switch configuration
If time permits
24.
Working in pairs, connect two PCs to one switch. Check everything is O.K. by using
ping. Now issue the following commands and note the changes from earlier in the
exercise when there was only one PC connected to the switch.
sh mac
_______________________________________
sh int
_______________________________________
sh ip int brief
_______________________________________
25.
Now move a PC from one port to another. Does ping still work? (It should but note
that we haven’t used VLANS yet.) Which of the above commands best shows the
change in port usage?
_______________________________________
_______________________________________
26.
Still working with a partner, connect a hub to one of the switch ports. Then connect
two PCs on the hub. Now look at the MAC address table. How many MAC addresses
do you see on the switch port with the hub attached?
_______________________________________
27.
On the switch run the following command. If the command doesn’t work ensure that
you are in privileged mode.
sh run
What does this show?
_______________________________________
28.
Does the source MAC address of a ping change as the ping passes through the
switch?
_______________________________________
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-19
Switch configuration
29.
Using Ethereal, capture packets for a while. What packets does the switch transmit
periodically? What source MAC address is used by these packets? If you move your
PC to another port does the source MAC address change?
_______________________________________
_______________________________________
_______________________________________
30.
Investigate the menus on HyperTerminal, in particular look at the transfer menu.
What are the first four items on this menu?
_______________________________________
_______________________________________
_______________________________________
_______________________________________
31.
The two most useful items are “Capture text” and “Send text file”. With these you can
copy and paste configurations to/from your PC. For example:
To copy a configuration
Capture text
sh run
Stop the capture text
An editor can then be used to change the configuration.
To download a configuration
enable
conf t
send text file can then be used.
Note: This can be used in the following way:
A central technical team produce configurations in a text editor. These configurations
are then copied to floppy disks that are then given to field engineers who use them on
site to configure the switches (using send text file).
Try this out by copying the configuration, editing the resulting text file to shut down a
port and downloading the new configuration. Check it worked.
32.
Try the above again but make sure enable and conf t are in the text file. What
would normally be needed in the text file after the enable?
_______________________________________
Introduction to Ethernet switching v1.2
© 2001 - 2003 Systems & Network Training Ltd
4-20