Using IP Aliases to Reduce Heartbeat Traffic

If there are a large number of CARP VIPs on a segment, this can lead to a lot of multicast traffic. One heartbeat per second is sent per CARP VIP. To reduce this traffic, additional VIPs may be “stacked” on top of one CARP VIP on an interface. First, pick one CARP VIP to be the “main” VIP for the interface. Then, change the other CARP VIPs in that same subnet to be an IP Alias type VIP, with the “main” CARP VIP interface selected to be their Interface on the VIP configuration.

This not only reduces the heartbeats that will be seen on a given segment, but it also causes all of the IP alias VIPs to change status along with the “main” CARP VIP, reducing the likelihood that a layer 2 issue will cause individual CARP VIPs to not fail over as expected.

IP Alias VIPs do not normally synchronize via XML-RPC configuration synchronization, however, IP alias VIPs set to use CARP interfaces in this manner will synchronize.