Configuring Catalyst 3750 /3750-E switches

Configuring Catalyst 3750 /3750-E switches

Hints & Tips:
If you wish to use a Cisco Catalyst 3750G – 12S (12 SFP ports) as a switch Master please refer to the SDM Templates section in this document.
Each member in the stack must have the same IOS image and feature-set. Otherwise upgrades of software become difficult, and may result in a breach of license.

Switch Stacks should confirm to the following standards:
Stack Numbering and Priority
The Stack Master will be the top switch in a stack and will have a member number of 1. All remaining switches will be positioned underneath the Stack Master and will be numbered sequentially.
The Master will have a priority of 15 and (where a stack of 3 or more switches exist) the second switch (member number 2) will have a priority of 10. All remaining switch members will have a default priority of 1.
Configuration Procedure

The following procedure should be used for configuring a stack:-
1. Before connecting switches in a stack confirm all switches are running the same IOS version. The minimum version to support LACP is 12.2(25)SEC. The minimum recommended version to support LLDP is 12.2(55)SE or later.

Do not connect switches to the network or to each other at this point.
2. Ensure that all switches have been cleared of any previous configuration (If switch is not new out of the box).

Hints & Tips:
To quickly check if a switch has been configured previously press and hold the Mode button for 3 seconds. When all of the LEDs left of the Mode button turn green, release the Mode button. If the LEDs left of the Mode button begin to blink after you press the button, release it. Blinking LEDs mean that the switch has already been configured

3. To prevent incompatible configurations, follow these steps on a previously configured switch that you plan to add to the stack:

STEP 1 Press and hold the Mode button, as shown below to delete the configuration
The switch LEDs begin blinking after about 2 seconds. If the switch is not configured, the mode buttons are all green.
STEP 2 Continue holding down the Mode button. The LEDs stop blinking after 8 additional seconds, and then the switch reboots.

4. Ensure all switches in the stack are powered off and connect the switches via StackWise cables. See the section below for detailed information on connecting the switches together.

5. Power the top switch first. Once this switch is powered up power the next switch below. Once this is powered up continue until all switches have been powered up. This will ensure the switches will be numbered incrementally from top to bottom.

6. Apply the configuration below to Switch 1 (Stack Master).

conf t
switch 1 priority 15
switch 2 priority 10
wr mem

Confirm the configuration is saved and then reload the switch

7. Apply the command below to maintain the same MAC address on the stack even if the stack Master fails. If you enter ’0’, the stack MAC address of the previous master is used until you enter the no stack-mac persistent timer global configuration command, which changes the stack MAC address to that of the current master. If you do not enter this command, the stack MAC address does not change. The new active master switch can continue to use the MAC addresses assigned by the old master switch, which prevents ARP and routing outages in the network.

conf t
stack-mac persistent timer 0
wr mem

Note: When you configure this feature, a warning message displays the consequences of your configuration: if the stack master is removed from the stack and re-used elsewhere in the network this will cause networking issues (duplicate MAC address) and could be difficult to fault find.

To check which MAC address is being used, and check if it’s persistent, you can use the show switch command

cr36-3750x-xSB (config)#stack-mac persistent timer 0
cr36-3750x-xSB #show switch
Switch/Stack Mac Address : 0026.5284.ec80
Mac persistency wait time: Indefinite
H/W Current
Switch# Role Mac Address Priority Version State
* 1 Master 0023.eb7b.e580 15 0 Ready
2 Member 0026.5284.ec80 10 0 Ready

8. Check the status of Stack with the ‘show switch’ command. Other useful commands are : –

show switch
show stack
show platform stack-manager all
show switch stack-port
show sdm prefer

At this point the configuration can now be applied to the Stack Master.

About the author

admin administrator

Leave a Reply