[c-nsp] nexus 5xx vpc peer keepalives

[Lincoln Dale]

>> the L3 (IP) based vPC keepalive is purely intended to assist in dealing with
>> split-brain if the vPC peer-link is non-functional.
>> 
>> having simultaneous failure of both would be an unusual circumstance,
>> particularly if you follow best-practice on the vPC peer-link itself..
> 
> This is what I had understood as well.  Is there any documentation about the information sent on the keepalive link?  Does the frequency remain the same, regardless of traffic on the box?  Even at 400ms intervals, is it still going to be a very small stream?

all the information contains is details on the vPC domains configured and their status.  no data-plane stuff.  the frames are quite small, <300 bytes if i recall, frequency is a fixed interval of between 400msec and 1second -- configurable.  yes its a small amount of data.

see <http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_1/nx-os/interfaces/configuration/guide/if_vPC.html#wp1385808>


as i said earlier, the vPC keepalive link is there purely to help ascertain if the vPC 'peer' is still alive in the event that all the vPC peer-link portchannel member links have failed.  its purpose is to prevent active-active in a split-brain manner.

the keepalive link is not mandatory - but certainly best practice would be for it to be operational as much as possible rather than having it on a network that didn't have the same availability as your primary data path.


cheers,

lincoln.