vPC looping prevention, any example with looping or duplicate packets ?

[thomastrupel]

Hello,

I'm new to vPC technology. I read many informations on the loop avoidance mechanism which rely on "logics implemented directly in hardware on vPC peer-link ports".

vPC loop avoidance rule states that traffic coming from vPC member port, then crossing vPC peer-link is NOT
allowed to egress any vPC member port; however it can egress any other type of port (L3 port, orphan port, ...).
The only exception to this rule occurs when vPC member port goes down.

I can't figure out why looping or duplicate packets may occur if packets are crossing peer-link.

Does someone can propose an example with looping or duplicate packets if packets are crossing peer-link ?

Best regards,

Thomas

[Mostafa Saleh]

Cause if the packet goes out from the client to NX-OS-A, then NX-OS-A will send the packet across peer link to NX-OS-B, so NX-OS-B must not send the packet out any of egress any vPC member port, or the loop will happen

cause the client will receive the packet which he originally sent

Hope it's clear now