Fabric Port Channel

Question

Hello,
Once in production, when adding cables in a Fabric PortChannel between an IOM and a FI, ¿is it needed to re-ack the chassis? (so that, we'll have downtime of the whole chassis). Or rather, as it is a Port-Channel the cables are detected automatically, so that it is not needed to re-ack, and so there's no downtime at all...which one is the correct statement?
Thanks,

Answer 1

Hello,
Let us consider following scenario on adding or removing links to existing deployment.
Initial deployment
UCSM 2.0, FI 62XX ,2208 IOM and 2 physical links with port channel configuration ( 2 link discovery policy )
Change
1) If additional links are added and if they need to be utilized and part of port channel, we need to re-ack the chassis.
2) If a link goes down,traffic is distributed across other links in port channel and does not require re-ack. Parameters like bandwidth, VIF ports that are calculated based on initial configuration remains the same.
3) If we physically remove the additional links between IOM / FI, re-acknowledment would create port-channel with original two links.Failure to re-ack will create over subscription ( bandwidth, available VIF ports ) of the network links.Re-ack is not mandatory but it creates appropriate configuration that matches required design criteria.
Caution
Adding or removing links  from a fabric port channel is disruptive and may affect the available amount of VIF namespace.
http://www.cisco.com/en/US/docs/unified_computing/ucs/sw/gui/config/guide/2.0/b_UCSM_GUI_Configuration_Guide_2_0_chapter_0101.html#concept_5D3D88341BFB43468B62B5A77876C67B
Padma