I wrote a blog post for NetScaler active/passive HA in Azure with multiple NICs two days ago, and I’ve been trying to figure out if this was the best way to do it. In the other post, I was using IPPattern in NetScaler to set the vServers to a /31 – which does work but that’s just because of how the underlying Azure infrastrucuture works (where machines outside of the VM – for example Azure LB – can only access the IP that has been assigned to the VM).
There is another way of doing this, which doesn’t require you to use a /31. The key is in configuring DSR (Direct Server Return) in Azure LB (also known as Floating IP). This will make it possible to use the same VIP on the NetScalers as the Frontend IP of the Azure LB – which saves IP-addresses and is easier to configure. This is the way Citrix has documented it and this is how their HA template does it.