Cisco 2960X stacking behaviour - is this normal ?

[SJ K]

Hi all,

I have 2 x 2960x stacked togethter.

Switch 1 is master

Switch 2 is member.

There are no addtional configurations done to configure the switch priority etc.

The election is done without manual intervention/configuration.

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Earlier, while having both the switches turn on,  we plug out all the stacking cables connecting to each of the switch at the same time and also do a reboot on each switch.

It is then noticed that the "Master"  led is turn on, on both switch.

On Switch 1, it is still the Master with "Ready" status and Switch 2 member with "Provision" status

On Switch 2, it has now become the Master with "Ready" status and Switch 1 member with "Provision" status

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a) It seems like now both the switches are thinking that they are the stack MASTER

b) Plugging back the stacking cable doesn't result in a MASTER re-election also, show switch remain status quo, with each switch thinking that they are the master. (also doesn't show any stack port connected etc console message)

Is this normal and how do i make both the switch detect one another again ?

Regards,

Noob

[Leo Laohoo]

If the stacking cable was connected to each switch while both switches are powered up, the entire stack reboots.  This is to be expected.

[SJ K]

Hi Leo,

The stacking cable was not connected when both the switches reboot.

So in this case, both switches will remain as master , and when the stack cable get reconnected back, there will be no re-election ?

How do we force the election then ?

Regards,

Noob

[Mark Malone]

when cables are connected if both switches believe they are the master just reboot one the election will occur and  one should go back to being the slave, when it boots up it should speak to the other switch and see that its already set for master , unless you have set a higher priority on the other switch it should revert back to member.

The cables must be connected for the switches to decide who is the master or else as you seen both will think they are

[SJ K]

Hi Mark,

But the behaviour in which

T1) remove stacking cable from both switch

T2) reboot both switch

T3) Both switch thinks itself is the Master

T4) plug back stacking cables , remain status quo (no changes) - is normal ?

When we plug back the stacking cable, there will be no re-election ?

I thought a re-election under such circumstances should occur

Is there anyway we can "force" a re-election without booting ?

Regards,

Noob

[Mark Malone]

Yes thats normal if theres no cable between them they dont know theres any slaves to elcet as members so they revert to default status which would be master

plugging cable back in wont cause re-election , think of it in real world a master switch fails in stack of 6 the election takles place a new master is formed for stack automatically , you still have to replace the old failed switch you dont want the whole stack to go into re-election again just because you put a new switch in the stack that could mean more downtime in a production networ of a huge stack

an election only takes place when the master is rebooted, if you put a new switch in with higher priority it wont become master until current master is rebooted , its to prevent the stack constanty breaking when theres a failure

[SJ K]

Hi Mark,

Even as you said, when we add a switch back in the stack, re-election will not occur until the current master is reboot. (which in my case, can reboot either switch (as both is master)).

But i am puzzled that even when i reconnect back the stacking cable to both switches. To the individual switch, the other switch's status is still  "Provisioned" instead of "Ready".  --> is this normal ?

There is basically no changes at all when the stacking cable is connected back. it is as each of the switch is not adware or does not care about the existence of another switch added back in the stack.

T1) break stack by pluggin out cable

T2) reboot both switch

T3) both switch now become master, and show each other as member with status "Provision"

T4) Plug back stacking cable

T5) no re-election took place +  no changes to switch "status", still showing as "Provision" -- is this normal ?

** To add-on, i have just restarted 1 of the switch, and when it boot up, it is still showing as Master. So both switches are still Master.

Regards,

Noob

[Mark Malone]

If you rebooted both of them and they are stacked together correctly 1 of them should have become slave and 1 master

what does it show on console does it say they are going into election when both rebooted ?

you can try force it by setting the priority of 1 of the switches to 1 and 15 for your master and provision both of them as well.If you reboot them after that and its still the same could be a buggy ios

2960x have a few notouriously bad images make sure your not running on an EX image , try be on a MD release as there more stable

[SJ K]

Hi Mark, Leo,

Sorry for the confusion. Maybe i did not clarify clear enough.. below is what was observed

T1) connected 2 switches with a stacking cable.

Switch 1 elected as Master  (status "Ready")  in show switch

Switch 2 elected as Member (status "Ready") in show switch

T2) disconnect the stacking cable and reboot both switches

T3) both switch are rebooted

Switch 1 shows itself as Master/Ready with Switch 2 as Member/Provision

Switch 2 shows itself as Master/Ready with Switch 1 as Member/Provsion

Both switch think that itself as the Master.

T4) connected back the stacking cable

Both switch status remain unchanged, showing each other as Member/Provision

T5) Rebooted Switch 2

When switch 2 come up, both Switch's status remain unchanged, thinking itself as the Master, and the other as Member/Provision.

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My doubts are in

at T4) even if there are no master re-election, why doesn't the "member" switch status get changed to "Ready", but still remains as "Provisioned"

at T5) even when i rebooted 1 switch, there is still no relection after the switch is up. Both still remains as Master

Does that means everytime i got a stacking cable fault, I have to reboot both switches then ?

Regards,
Noob

[Mark Malone]

Hi i think answered that in last post if both at default settings and both showing as master if you reboot both only 1 should be master after reboot, have you tried setting the priority, it might be your IOS  rather than stacking cable

are your stack cables connected port 1 - 2 on each switch rather than 1-1

when both switches come online after reboot you should see the elcetion occurring in the console output do you see that ?

[SJ K]

Hi Mark,

When both switch are showing as master and if I rebooted just 1 of them, when the rebooted switch is up, there is no election taking place.

Both will remain as master still. I have to reboot 2 switches to get the election running.

The stacking cable are connected 1-1 and 2-2.

Thus, i am not sure why rebooting just 1 switch doesn't work.

This also implies that if i have a stacking cable connectivity issue and the stack breaks having both switch thinking that they are master - I have to reboot the 2 switches together - which i think is not the correct behavior. ( can't i just reboot 1 switch ?)

Please let me know your thoughts

Regards,

Noob

[Mark Malone]

The election should occurr when you just reboot the master it should not require to boot 2 switches to get the election going, what ios are you running on?

can you post

sh switch stack-ring activity

sh switch detail

[Leo Laohoo]

both switches will remain as master , and when the stack cable get reconnected back, there will be no re-election ?

Ok, let me put it this way ... You have two switches.  Both are powered on and both are not connected to the stack.  

Connect both of them (still powered up) with a stacking cable and both both of them will reboot.  Why?  Because the two units will go into a forced election.  This behaviour is to be expected.