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Cisco 3750Es - making a stack

I ran into an odd thing - two Cisco 3750E switches each with 48 ports - but with configuration for 96 ports 1/0/1 - 48 2/0/1 - 48. They IP addresses were the same and in troubleshooting I found DUP IP errors. It looks as though perhaps at some point in the past they were a stack w two members.

I am sending out a couple of stacking cables. But I can't manage the switches because the IP conflict keeps bumping me off SSH.

My question - since I can't lab this out - should attaching stack port 1 on SW1 to stack port 2 on SW2 cause the config from SW1 to sync with SW2? Or is there some config that would need to be added to SW1 or SW2 for stacking to do its thing? In the end I want one config, one set of IP addresses.

Thank you!

SOLUTION

Predrag Jovic

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Andy Ransom

First, I would verify licensing is correct for stacking. Even if they were a stack in the past, licensing could of course be changed. Unless Cisco has changed it in the last few years, a switch running IPBase license can stack with anything other than LANBase - which can only stack with another LANBase licensed switch.

As long as the licensing is right, the stacking will happen automatically, as will selection of stack master. It will typically automatically select the stack master; the other will possibly reload, if needed, to apply configuration from the master.

IOS version should also be the same on both, to ensure full compatibility. Major version number differences are not compatible, and Minor version number differences are considered partially compatible.

I recommend either backing up the config you want as primary, or manually setting a the master to be highest stack priority before adding the other switch, to be sure automatic selection does not pick the wrong one and lose some needed settings. The official Cisco recommendation is to set the priority setting.

A good document related to stacking 3750 including setting stack priority is at https://www.cisco.com/c/en/us/support/docs/switches/catalyst-3750-series-switches/71925-cat3750-create-switch-stks.html

Because you already have a config on both devices, be sure to see the section "Add a provisioned Switch to a Switch Stack"; the direct link for this section is https://www.cisco.com/c/en/us/support/docs/switches/catalyst-3750-series-switches/71925-cat3750-create-switch-stks.html#anc19

amigan_99

ASKER

That's very clever - hard coding the ARP entry on the WAN router. I have the two Mac addresses now and I'll try that late in the day when folks have gone home.

amigan_99

ASKER

While I can't SSH to the two switches. I am able to pull information by going through the web interface. But looking at which mac address is active at the time of execution then I know which switch I'm on. Both members perceive themself as master. SW1 has the lower mac address and the highest priority. Their hardware and firmware versions match. So I think just cabling these puppies up will get me to a better state. Just need to disconnect the trunk between the two. Can't believe consultants left these in this state.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_55_se/configuration/guide/3750xscg/swstack.html#77443

Switch/Stack Mac Address : b0fa.eb12.6a00
H/W Current
Switch# Role Mac Address Priority Version State
----------------------------------------------------------
*1 Master b0fa.eb12.6a00 10 3 Ready
2 Member 0000.0000.0000 0 0 Provisioned

Switch/Stack Mac Address : b0fa.eb29.b400
H/W Current
Switch# Role Mac Address Priority Version State
----------------------------------------------------------
1 Member 0000.0000.0000 0 0 Provisioned
*2 Master b0fa.eb29.b400 1 3 Ready
Switch/Stack Mac Address : b0fa.eb29.b400

ASKER CERTIFIED SOLUTION

Andy Ransom

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