Cisco Cisco Nexus 5010 Switch Guida Alla Risoluzione Dei Problemi
Loop avoidance
For broadcast/unknown unicast/multicast frames coming into vPC primary switch, they will be sent out with a
FTAG of 256 across the peer−link. When the vPC secondary switch gets this frame across the vPC peer−link,
it inspects the FTAG and since its 256, the vPC secondary switch will only send it out to FTAG 256 members
which will be orphan ports only. For flood traffic from vPC secondary, it will be sent with FTAG of 257 and
when the vPC primary switch gets this frame, it sends the received flood frame only to members of FTAG 257
which will be orphan ports only. This is how Carmel based switches implement vPC loop avoidance.
FTAG of 256 across the peer−link. When the vPC secondary switch gets this frame across the vPC peer−link,
it inspects the FTAG and since its 256, the vPC secondary switch will only send it out to FTAG 256 members
which will be orphan ports only. For flood traffic from vPC secondary, it will be sent with FTAG of 257 and
when the vPC primary switch gets this frame, it sends the received flood frame only to members of FTAG 257
which will be orphan ports only. This is how Carmel based switches implement vPC loop avoidance.
In order to deep dive L2MP/FTAG based forwarding of flood frames across peer−link, this topology is used:
N5K−C5596UP−109 and N5K−C5596UP−100 are a vPC pair of Nexus 5596 switches running NX−OS
5.2(1)N1(2a). N5K−C5596UP−109 is the vPC primary switch and N5K−C5596UP−110 is the vPC secondary
5.2(1)N1(2a). N5K−C5596UP−109 is the vPC primary switch and N5K−C5596UP−110 is the vPC secondary