Catalyst 2960S stacking link failure

[abdul-ghafu]

would like to know more on the stacking features for the 2960s switches.

Assuming only using one stacking links for two 2960s to stack together.

what happens when the stacking link fails?

will it break into two logical switch?

had checked the resource for flexstack FAQ as below, that it will continue to remain as a single unit,but it didnt explain further.

Q. Can FlexStack operate with only one stack link operational?

A. Yes. FlexStack can operate with a single stack link. When operating in  this mode, the stack is not operating in a redundant fashion. If each  member in the stack connects to two separate members forming a ring, the  operational loss of a single member will not break up the stack. When  FlexStack is connected in a fully redundant fashion, as it is when a  ring is formed with the FlexStack cables, it will continue to operate a  single unit when it loses a member or a single stack link failure  occurs.

[Shashank Singh]

Hi Ghafur,

FlexStack is same as the regular stackwise concept. Each switch has two stack ports and hence can be connected to two other switches. However the stack can run, even with a single stacking cable on each switch.

In case you connect two cables per switch, the stack forms a ring and this doubles the bandwidth of the backplane and also prevents stack failure in case single link fails (as the stack can still survive on the other cable).

However, in case you have only one stack cable connected between two switches, in case of stack cable failure, the stack will break into two standalone switches. This hold true for both Stackwise and new FlexStack technology.

Hope this helps,

Shashank

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[abdul-ghafu]

Hi Shashank,

Thanks so much for your response! =)

But i am bit confuse as the one mentioned in the FAQ saying that it will maintain as a single unit should the link fails,

Can you assist to explain to me, i am not clear on that part. Pardon me for that.

Also how about the IP addressing, as the stack will be managed as a single IP, and if the link fails, will the two switches having the same IP, will there be any issue to that?

[Shashank Singh]

Hi Ghafur,

The stack will remain as a single unit in case of link failure only when you connect both the stack cables on the switches and only one of the links fail. This is because the stack can still remain as a single unit just on one stack cable. If you just connect one stack cable behind the switches, stack wont remain as a single unit if the link fails.

Stack master will have the IP as long as the the switches are stacked and entire stack can be managed with that IP. In case the switches become standalone due to link failure, just the master switch will have the IP. All the member switches will not have any IP.

Hope that helps,

Shashank

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[abdul-ghafu]

Hi Shashank,

Big thanks for the fast response!!!

ok now i understand better, appreciate that alot,

Stack master will have the IP as long as the the switches are stacked and entire stack can be managed with that IP. In case the switches become standalone due to link failure, just the master switch will have the IP. All the member switches will not have any IP. --> so meaning the unassigned Ip switch will not be accessible?

[Shashank Singh]

Hi Ghafur,

Yes the unassigned IP switch will not be accessible in case stacking fails.

Cheers,

Shashank

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[abdul-ghafu]

Hi Shashank,

Thanks for being a helpful support to me ,

Also you got any resources/documentation on that or explaining on the stacking features, so i can learn more on the stacking features.

[Shashank Singh]

Hi Ghafur,

I was a pleasure helping you

2960S flexstack description, usage, and best Practices are available at:

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps6406/white_paper_c11-578928.html

Cheers,

Shashank

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