Process for replacing a failed master switch in a Cisco 3750 switch stack
1. Upgrade or downgrade the software on the replacement switch to match the rest of the switch stack
The version of IOS running on the switch must match the other switches in the stack exactly. IOS images used on CHPC switches can be found on the TFTP server, megatron.chpc.utah.edu in /tftpboot/images/cisco . To see what version is running on one of the functional switches, use show version:
delicate_stack2#show version
Cisco IOS Software, C3750 Software (C3750-IPBASEK9-M), Version 12.2(44)SE, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Sat 05-Jan-08 00:29 by weiliu
Image text-base: 0x00003000, data-base: 0x01440000
ROM: Bootstrap program is C3750 boot loader
BOOTLDR: C3750 Boot Loader (C3750-HBOOT-M) Version 12.2(25r)SEC, RELEASE SOFTWARE (fc4)
delicate_stack2 uptime is 3 hours, 17 minutes
System returned to ROM by power-on
System restarted at 09:31:25 MDT Fri Jun 25 2010
System image file is “flash:c3750-ipbasek9-mz.122-44.SE/c3750-ipbasek9-mz.122-44.SE.bin”
….. (output omitted) ….
The line “System image file is …” will show the image name that needs to be used. Find this image name (with a “-tar” in it) either on megatron or on the Cisco web site.
Once you have identified which version of IOS to use, connect the switch to the network using an IP address that is available (such as a moria address). To do this, bring up a VLAN interface on VLAN1 and connect the switch to the network. VLAN1 is used because all of the ports on the replacement switch will already be in that VLAN, and all you have to do is find a port on the network and plug in. Also, turn off spanning tree to speed up bringing up the link.
(config)# int vlan 1
(config-if)# ip address 172.30.2.209 255.255.0.0
(config-if)# no shut
(config-if)# exit
(config)# no span vlan 1
Make sure you can ping out:
delicate_stack2(config)#do ping 172.30.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.30.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/203/1006 ms
Also, make sure you can ping megatron:
delicate_stack2(config)#do ping 155.101.3.209
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 155.101.3.209, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/203/1006 ms
Next, upgrade the replacement switch using the archive command from privileged-exec mode:
delicate_stack2# archive download-sw tftp://155.101.3.109/images/cisco/3750/c3750-ipbasek9-tar.122-44.SE.tar
2. Change the replacement switch number to 1
First, figure out what the replacement switch’s number is:
delicate_stack2#sh switch
Switch/Stack Mac Address : 0017.5a33.f180
H/W Current
Switch# Role Mac Address Priority Version State
———————————————————-
*2 Member 0016.9dba.9800 14 0 Ready
This switch’s number is 2
(config)# switch 2 renumber 1
You’ll be asked to confirm the change, and then get a message about reloading the switch.
Reload the switch and continue with step 3 below.
3. Change the switch priority
The master switch in a stack is the one with the highest priority. To make sure that this new switch becomes the master, make its priority the same or higher than the failed switch. If you don’t remember what the failed switch’s priority is, just run show switch on one of the remaining functional switches and make sure that the priority that you assign to the replacement master switch is higher than the priority for the slave switches. Set the priority like this:
(config)#switch 1 priority <priority>
4. Power down the entire stack and disconnect the failed master switch
The entire stack will lose its configuration when the master switch is replaced. This is okay, because we regularly back up our configs, right? Make sure to note the pattern of how the cables plug in so that you can plug them in to the new switch in the same way.
5. Connect the new master switch and power up the stack
Connect everything up. Make sure to use a screwdriver to tighten up the stacking cables, as they have pretty shallow receptacles.
6. Configure the uplink ports and assign an IP address to the master switch
In order to restore the backed-up configuration, you’ll have to get some kind of network access working on the switch. Usually, this will mean configuring a portchannel and setting up some VLANS. Check the configuration on the remaining functional switches in the stack to see what VLANs to use, etc.
7. Pull down the backed-up configuration from the TFTP server
delicate_stack2# copy tftp run
and follow the prompts for TFTP server and file name. Once the configuration is finished copying, everything should be up.
8. Verify stacking
Verify that the stack is configured as expected. Use show switch and make sure that switch 1 is the master:
delicate_stack2#show switch
Switch/Stack Mac Address : 0017.5a33.f180
H/W Current
Switch# Role Mac Address Priority Version State
———————————————————-
*1 Master 0017.5a33.f180 15 0 Ready
2 Member 0016.9dba.9800 14 0 Ready
3 Member 0024.5038.e200 13 0 Ready
Make sure to save the configuration before you leave:
delicate_stack2# wr
Building configuration…
[OK]
Process for replacing a failed slave switch in a c3750 switch stack
1. Upgrade or downgrade the software on the replacement switch to match the rest of the switch stack
The version of IOS running on the switch must match the other switches in the stack exactly. IOS images used on CHPC switches can be found on the TFTP server, megatron.chpc.utah.edu in /tftpboot/images/cisco . To see what version is running on one of the functional switches, use show version:
delicate_stack2#show version
Cisco IOS Software, C3750 Software (C3750-IPBASEK9-M), Version 12.2(44)SE, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Sat 05-Jan-08 00:29 by weiliu
Image text-base: 0x00003000, data-base: 0x01440000
ROM: Bootstrap program is C3750 boot loader
BOOTLDR: C3750 Boot Loader (C3750-HBOOT-M) Version 12.2(25r)SEC, RELEASE SOFTWARE (fc4)
delicate_stack2 uptime is 3 hours, 17 minutes
System returned to ROM by power-on
System restarted at 09:31:25 MDT Fri Jun 25 2010
System image file is “flash:c3750-ipbasek9-mz.122-44.SE/c3750-ipbasek9-mz.122-44.SE.bin”
….. (output omitted) ….
The line “System image file is …” will show the image name that needs to be used. Find this image name (with a “-tar” in it) either on megatron or on the Cisco web site.
Once you have identified which version of IOS to use, connect the switch to the network using an IP address that is available (such as a moria address). To do this, bring up a VLAN interface on VLAN1 and connect the switch to the network. VLAN1 is used because all of the ports on the replacement switch will already be in that VLAN, and all you have to do is find a port on the network and plug in. Also, turn off spanning tree to speed up bringing up the link.
(config)# int vlan 1
(config-if)# ip address 172.30.2.209 255.255.0.0
(config-if)# no shut
(config-if)# exit
(config)# no span vlan 1
Make sure you can ping out:
delicate_stack2(config)#do ping 172.30.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.30.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/203/1006 ms
Also, make sure you can ping megatron:
delicate_stack2(config)#do ping 155.101.3.209
Type escape sequence to abort.
Sending 5, 100–byte ICMP Echos to 155.101.3.209, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/203/1006 ms
Next, upgrade the replacement switch using the archive command from privileged-exec mode:
delicate_stack2# archive download-sw tftp://155.101.3.109/images/cisco/3750/c3750-ipbasek9-tar.122-44.SE.tar
2. Change the switch number to match whatever the failed switch number was
First, figure out what the replacement switch’s current number is:
delicate_stack2#sh switch
Switch/Stack Mac Address : 0017.5a33.f180
H/W Current
Switch# Role Mac Address Priority Version State
———————————————————-
*2 Member 0016.9dba.9800 14 0 Ready
This switch’s number is 2
(config)# switch 2 renumber <switch number from the failed switch>
You’ll be asked to confirm the change, and then get a message about reloading the switch.
Reload the switch and continue with step 3 below.
3. Change the switch priority
The master switch in a stack is the one with the highest priority. To make sure that this new switch does not become the master, make its priority lower than the master switch. You can run show switch on the master switch to see what the current priorities of the other switches in the stack are. Set the priority like this:
(config)#switch 1 priority <priority>
4. Power down the failed switch and disconnect it from the stack
The other switches in the stack can stay up and passing traffic while you remove this switch. Make sure that you note the position of the stacking cables.
5. Connect the new switch and power it up
Connect everything up. Make sure to use a screwdriver to tighten up the stacking cables, as they have pretty shallow receptacles.
6. Verify stacking
Verify that the stack is configured as expected. Use show switch and make sure that switch 1 is the master:
delicate_stack2#show switch
Switch/Stack Mac Address : 0017.5a33.f180
H/W Current
Switch# Role Mac Address Priority Version State
———————————————————-
*1 Master 0017.5a33.f180 15 0 Ready
2 Member 0016.9dba.9800 14 0 Ready
3 Member 0024.5038.e200 13 0 Ready
Make sure to save the configuration before you leave:
delicate_stack2# wr
Building configuration…
[OK]
Other Notes
Find the serial number on a switch
Using show inventory you can get the serial number info from all of the switches in the stack:
delicate_stack2#show inventory
NAME: “1”, DESCR: “WS-C3750G-24T”
PID: WS-C3750G-24T-S , VID: V07, SN: CAT1010Z1LX
NAME: “2“, DESCR: “WS-C3750G-24T”
PID: WS-C3750G-24T-S , VID: V06, SN: CAT0951N3DS
NAME: “3“, DESCR: “WS-C3750G-24T”
PID: WS-C3750G-24T-S , VID: V07, SN: FDO1248X3LN
Back up the configuration to the CHPC TFTP server
When you are finished replacing everything, make a backup to the CHPC TFTP server at megatron.chpc.utah.edu. Create a directory on megatron in /tftpboot/configs with the current date, in the format of YYYY-MM-DD. Usecopy run tftp to get it done:
delicate_stack2#copy run tftp://155.101.3.109/configs/2010-06-25/delicate-stack2
—Reference from https://wiki.chpc.utah.edu/display/CHPC/Cisco+3750+Stacking+configuration+notes+and+processes
Cisco StackWise and StackWise Plus Technology
https://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps5023/prod_white_paper09186a00801b096a.html
Creation and Management of Catalyst 3750 Switch Stacks
https://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_example09186a00807811ad.shtml
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