2960x stack - add another member?

[louis0001]

Hi,

we have 2x 2960x 48 port switches configured as a stack. I now need to another member.

I know I simply disconnect one of the existing flexstack cables and then add the other member.
I'm also aware of the minor outages and how to connect the cables for a 3 stack configuration.

I understand that when I disconnect the cable, the switches will go into non redundant mode.
However, I have 2 SPF ports (1 on each switch stack member) configured as a port channel going to another switch.

Would there be any adverse effect with the above etherchannel when I disconnect one of the flexstack cables and place the stack into non redundant mode?

Louis

[Philip D'Ath]

Assuming you have the normal ring configuration (so every switch has two Flexstack connections), then only unplugging one at a time wont break it.

[louis0001]

I guess what I'm really asking is what does "non redundant mode" mean?

Does it simply mean that the members are not redundant because there is only one flexstack cable running the stack rather than two?
So by pulling one of the flexstack cables, the stack still runs and as an example, plugging in a new member with only one cable attached to it will actually allow the whole stack to work and the new member to join but the stack won't be fully redundant until the second cable is plugged in?

I know the above is not the correct way to add the new member but is only an example in an attempt to understand why the port channel on each separate switch is not affected.

[Philip D'Ath · Accepted solution]

"non redundant" means it can not handle an additional failure (aka a second failure).

Your statements above are correct.

[louis0001]

Well, after a bit of reading etc i added the new member which was really simple. Although Cisco states there will be two minor interruptions (one when you unplug a flexstack cable and then one when the new member is added), I did not witness any interruption whatsoever so it went in a dream. Etherchannel wasn't affected in the slightest although I did learn that Cisco do not recommend putting a redundant uplink on the stack master.

[Philip D'Ath]

Well done!  What makes you think the stack master should not have a redundant link?  That sounds very wrong to me.

[louis0001]

Originally, my setup was 2 members in the stack. Each member was connected to another core switch via an ether channel.

My setup is now 3 members in the stack. Cisco recommends putting a 2 channel etherchannel connection on the switch that is not the master in a 3 member+ config.

It's in this doc:

http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-2960-x-series-switches/white_paper_c11-728327.html

Towards the bottom under Recommended Deployment Strategies For Building Flexstack

[Adel Barashed]

This stack provides only half of the possible bandwidth between members and does not have redundant connections. Only the middle member has full stack bandwidth. The top and bottom members are operating at half the fully redundant stack bandwidth.

[Adel Barashed]

FlexStack Member Addition When a new switch joins an existing stack (that is, a stack that has already elected a master), then the new switch will be rebooted after it joins. This is to remove any old configuration. When the new switch completes the reload, it will become a member of the existing stack. The new member will be assigned the next available unused member number if it was not preprovisioned. Preprovisioning of switch members is covered in the Cisco Catalyst 2960-S and 2960-X software configuration guide on Cisco.com. This behavior is covered in more detail in subsequent sections

Ref:- Ref:- http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-2960-x-series-switches/white_paper_c11-728327.pdf

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This example will show how to add switches to the bottom of an existing stack of switches.

1. Place the new switch in its final location. Do not insert the power cord. To minimize downtime, complete all cabling that would be required of any switch placed into production at this time.

2. Insert the FlexStack module in the back of the new member.

3. Disconnect the FlexStack cable from the existing member just above to the new member. This would be the cable that is connecting the bottom member with the top member. You will need this to connect the new member located at the bottom of the stack to the member at the top. a. When the FlexStack cable is disconnected, this is when the stack enters into a nonredundant mode.

4. Connect the new member with a FlexStack cable to the member just above. The FlexStack port used to connect one member to another is not important. Stack members should be connected to each other any way that makes cable management easier for the network administrator.

5. Connect another FlexStack cable to the member at the top. Make sure that all cables are connected properly. A light tug on the FlexStack cable will make sure that it is properly seated.

6. Connect the AC power cord to the new member. It will power on. It will take a few minutes for the new member to complete the boot process.

7. The new member will join the existing stack as a member, not the master. a. When the new member completes the boot process, this is when the stack enters into a fully redundant mode once again.

8. All the FlexStack links will be operational if all the connections were made properly.

Ref:- http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-2960-x-series-switches/white_paper_c11-728327.pdf

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