How does VCS check IF different heartbeat NICs are in same network?

[xhawk]

Cluster-A syslog shows:

Jun 23 07:22:11 IMDB1 vmunix: LLT WARNING V-14-1-10498 recvarpreq cross links? links 1 and 0 of node 1 connected to same network?
Jun 23 07:27:11 IMDB1 vmunix: LLT WARNING V-14-1-10498 recvarpreq cross links? links 1 and 0 of node 1 connected to same network?
Jun 23 07:32:11 IMDB1 vmunix: LLT WARNING V-14-1-10498 recvarpreq cross links? links 1 and 0 of node 1 connected to same network?
Jun 23 07:57:11 IMDB1 vmunix: LLT WARNING V-14-1-10498 recvarpreq cross links? links 1 and 0 of node 1 connected to same network?
Jun 23 08:12:11 IMDB1 vmunix: LLT WARNING V-14-1-10498 recvarpreq cross links? links 1 and 0 of node 1 connected to same network?
Jun 23 08:17:11 IMDB1 vmunix: LLT WARNING V-14-1-10498 recvarpreq cross links? links 0 and 1 of node 1 connected to same network?

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The heartbeats NICs are lan901 and lan902.

I know VCS heatbeats are broadcast packets. and LLT on each system in the cluster sends heartbeat packets out on all configured LLT interfaces every half second.

My questions are:

1) How, by what mechanism, does VCS check IF different heartbeat NICs are in same network (VLAN)?

   To which kind of address (MAC or OS device names) does the check signals send?

2) How often does it check if NICs are in same VLAN?

3) We have other systems Cluster-B and Cluster-C, they have almost the same network configurations (To be verified), but their syslogs do not have these kind of warnings.Why?

Thanks in advance!

[mikebounds · Accepted solution]

As you say heartbeats are broadcast so if a heartbeat on link1 receieves a heartbeat from link2 it knows the heartbeats are in the same networks (crossed links)- so I don't think VCS specifically does a periodic check for crossed links - LLT just complains if it receives a heartbeat from a different link - and it know this as the MAC address is used for the heartbeat.  I have seen configs where the messages for cross links ae intermittent so I guess in a good network, the right NIC receives the heartbeat packet, but maybe in a congested network, the packet sometimes gets to the other NIC, which is why you may not be seeing the error message in your other cluster.

Mike

[xhawk]

Thanks, Mike, you make this clear.