keepalived - multiple VRRP instances vs. 1 instance with multiple VIPs

Question

I need keepalived to manage several Virtual IP addresses on the same network interface.

I'm wondering, what are the advantages and disadvantages of having keepalived configured with different VRRP instances (let's say 1 VRRP instance per 1 Virtual IP) as oppose to have just one VRRP Instance with all Virtual IPs in it?

I should mention that all of the Virtual IPs are on the same VLAN.

Answer 1

In both cases, when the MASTER fails, all VIPs will fail over together, as expected in such a case.

On the other side, changing priority won't have the same impact: - with a single instance, changing priority makes all VIPs fail over - with one instance per VIP, changing priority makes the single VIP fail over

So the question to ask is: do you need to fail over a single VIP at a time?

Answer 2

It is important to understand what the failure condition for the OP is, specifically if using a health check script.

There may be no need to migrate all your IP addresses for different instances if a single service failed.

10.1.0.1 webserver ha virtual 10.1.0.2 mysql ha virtual 10.1.0.2 imap/pop ha virtual.

If the imap/pop ha virtual failed, yes you want it to move to a healthy machine interface, but if floated mysql and webserver which are testing healthy this is a needless service interruption for those services, just because you lost pop.

Yes, if the interface or network itself failed, all three would travel as vrrp would trump the service health checks.