Internal LAN - No port channels (chassis discovery policy)

[Dragomir]

I noticed I have a one link linking group preference of none set on my chassis/fex disovery policy

then I noticed that under the LAN tab, under internal LAN, there is no port channel set.

When I change the policy to 1 link and port channel and reack the chassis, I see 4 ports under the port channel in internal LAN.

Is it necessary to change the policy to port channel or can i just leave it at none? 

What would be the difference?

[Walter Dey · Accepted solution]

Best practise is to use port-channel between IOM and FI; (this requires second generation hardware for FI (62xx) and IOM (220x)

If your discovery policy is set to 1, and you ack the chassis, it will automatically create a pc of 4 links.

[Dragomir]

IF i change the policy to port channel and reack the chassis, will that affect the hosts?

[Walter Dey]

Reack the chassis disrupts any traffic from the IOM to FI for about 20-25 seconds. No server will be rebooted; most OS can tolerate this outage of traffic; however, if you run e.g. a heavy loaded database server, it might not like it.

[Dragomir]

Does it support only even number of links from the iom to the FI?

Does it support 3 links per iom?

[Walter Dey]

NO -> Link Discovery Policy can be only 1, 2, 4, 8, depending of the IOM model

see Table 7: Chassis/FEX Discovery Policy and Chassis Links

http://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/sw/gui/config/guide/2-2/b_UCSM_GUI_Configuration_Guide_2_2.pdf