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Beginner

Chassis Discovery Policy....

If you have 4 5108 Chassis can you have 1 chassis with 4 links per fex and 3 with 2 links?  I would imagine the answer to that is no, as the policy is system wide.  Personally I really wanted the policy to be more like MLPP and be a minimum set of links to consider a chassis up but that all connected links would be utilized. 

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Enthusiast

Re: Chassis Discovery Policy....

Yes, you can have some chassis with 2 and some with 4. Set the chassis discovery policy to 2 and on the chassis with 4 uplinks you will have to acknowledge them.

Take a look at this blog post

http://www.unifiedcomputingblog.com/?p=167

Highlighted
Beginner

Re: Chassis Discovery Policy....

Thanks for the reply, and the testing you did seems interesting.  When we built the system out a few weeks ago we had the discovery policy set to 1 but brought up 2 links per FEX.  TAC told us that you had to change the discovery policy to 2 in order for the system to use the links, or else the link would not be used and there would be an alert.

I can't test this out right now but I may try on another system and see what the results are.

Highlighted
Enthusiast

Re: Chassis Discovery Policy....

Hi,

The chassis discovery policy defines the minimum number of links (1,2 or 4) the UCSM expected or wants to see between the FI and the chassis when the chassis is being discovered. See it as the minimum links you need from the FI to the chassis, you can have the policy set to 1 or 2 and have 4 links in actual or set to 1 and have 2 links or 4 links in actual. When the chassis is discovered or re-acknowledged all the links connected will be bought online on the FI and the pinning to the vnic from the blades will be distributed accordingly.

./Abhinav

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Beginner

Re: Chassis Discovery Policy....

Thanks that is what I thought but it was funny to hear tac say something totally different.  I mean 'Chassis Discovery Policy' does sound more like a minimum link policy than anything else and when TAC said it was the amount of links used I was not 100% sure of that.

Highlighted
Cisco Employee

Re: Chassis Discovery Policy....

The chassis link discovery policy dictates the minimum number of physical links between the IOM and FI (server ports). This UCS policy based management mechanism allows the system designer to specify a configuration requirement that must be met in order to allow a chassis to join a cluster. The default setting is 1 server link. If your UCS design required a minimum of 20G per IOM, you would set the link discovery policy to 2. If a chassis was mis-cabled, the chassis would not discover and force someone to investigate the issue before allowing it to join the cluster and go into production.

Where this gets misunderstood is when you have a link discovery policy of 1 and have 4 links going to each IOM and you notice that the chassis is only running on one link per IOM. In order to bring all links up you MUST do a chassis acknowledegment. The chassis link discovery policy allows it onto the cluster, it does not automatically bring up all links and pin them to specific slot postions. Once a chassis has met the link discovery policy and you perform a chassis acknowledgement you will bring up all of the links (1,2,or 4) and pin the slots to those links.

So, in the case of multiple chassis in the same cluster where some have 2 links, some with 4 links, you can set the link discovery policy to 1 or 2 as long as you acknowledge the chassis. If the policy was set to 4 in this case, no amount of chassis acknowedege would bring those chassis with only 2 links into the cluster (they would not discover)

Highlighted
Beginner

Re: Chassis Discovery Policy....

That is what I thought.  Appreciate everyone's input. 

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