Hi,
We have a setup with two pairs of Nexus 7000 in the following topology:
NX7K-1A ---------- NX7K-1B
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| |
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NX7K-2A ---------- NX7K-2B
NX7K-1A|B is one pair, and NX7K2-A|B is the second pair.
Unfortunately we didn't configure the two pairs with a unique vPC domain id, which have turned out to cause some problems especially when enabling the peer-switch feature and MSTP.
In short we are using MSTP with all VLAN's assigned to MIST1. It works in a loop-free topology, where we disable (shutdown) one of the interfaces between the two Nexus pairs, but when enabled a loop is formed. When in a loop-free topology (might also be the case when not in a loop-free topology), the two Nexus pairs, each using peer-switch, sees themselves as root, even though they have different priorities (4095 / 8192 respectively) and the one and only active interface between the two Nexus pairs, is in ALTN/BLK in MIST0 (CST), which basically cuts MIST0 in two.
The documentation is pretty vague on what specific kind of problems two identical vPC domain id's leads to, other than some port-channel issues.
The vPC system-mac is created using 00:23:04:ee:be:<domain-id> which properly is the main cause of the problem, when having two vPC pairs with the same domain id in the same L2 domain. The documentation states that you could configure a static vPC system-mac, and since the domain id is local to the Nexus, would this solve the problem? Or are there other things derived from the vPC domain id?
