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Virtual Connect SmartLink and LACP question

chuckk281
Trusted Contributor

Virtual Connect SmartLink and LACP question

Matthew had a link aggregation question:

 

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I have had the following question from one of my partners Solution Architects;

 

Can you let me know if I am correct in thinking that you don't need SmartLink if a VC module is LACP connected to two Cisco switches if they are using vPC?

 

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(Couldn’t find a VC to Nexus 5000 version, so imagine the server is a VC FlexFabric module with LACP, and that the Nexus 2000 aren’t there.  The link between the Nexus 5000 is VCP peer, as per http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9670/configuration_guide_c07-543563.html.)

 

I think they are correct but I am no expert on the matter, and I haven’t been able to find any documentation to say one way or the other.

 

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Reply from Vincent:

 

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Short answer: just enable SmartLink

 

Long answer: the interest of SmartLink is somewhat independent of whether the upstream switches are joined at the hip with vPC or not, although vPC makes it less likely that SmartLink will kick in. You presumably still have uplinks coming out of 2 VC modules, and therefore 2 port-channels on the Cisco side since VC doesn’t do distributed LACP yet. On the VC side you can either create 2 VC networks (or SUS), one for each port-channel, that’s an Active/Active config, or a single network (or SUS) with both port-channels, that’s an Active/Standby config. In the Active/Active case, you want SmartLink enabled to trigger a NIC failover in the server if a port-channel goes down (although that’s unlikely to occur because your port-channel is distributed on 2 different physical switches). In the Active/Standby case, SmartLink is less useful because the failover happens at the VC level, and it could be slightly harmful because if all uplinks go down on both sides (which would trigger SmartLink), it would cut off downlinks on both sides as well and therefore cut off even communication between blades in the enclosure, but if that happens your servers can no longer communicate with the outside anyway and that’s probably a bigger problem.

 

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Other comments or suggestions?

2 REPLIES
chuckk281
Trusted Contributor

Re: Virtual Connect SmartLink and LACP question

Some info from Chris:

 

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In an active / active config you will need smart link. VCP would allow the creation of a SUS with and Port channel connected to both switches.

Smart link would disable any Vnets from that SUS if both links went down. Ideally you would need two SUSes, one for VC1 connected to both switches with its own LACP port channel, and the same for VC2 on a different SUS and LACP port channel.

At the OS and Nic level you would have two paths to the network.

 

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Avi
Occasional Advisor

Re: Virtual Connect SmartLink and LACP question

You can also refer these guides which has detailed information :

 

Virtual Connect CLI Network Management Guide with Nexus vPC Configuration :
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c03178759/c03178759.pdf

Virtual Connect and HP A-Series switches IRF Integration Guide :
http://bizsupport1.austin.hp.com/bc/docs/support/SupportManual/c02843088/c02843088.pdf

HP Virtual Connect Flex10 & FlexFabric CISCO Nexus 5000 & 2000 series Integration :
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c02656171/c02656171.pdf

I am an HP employee