Response from Nick Bond, System Engineer, Stingray Business Unit, Riverbed.
Hi,
as you have probably already noticed, you can only have one external IP address raised on an EC2 instance.
This limits the capability of the TM cluster. Your only option here is to increase the number of Elastic IP members in the Traffic IP Group (and to advertise these addresses via DNS). What you need to be careful of, is that you have sufficient standby TMs to take over from any failed machines.
So for example in your 4 machine cluster, you could have two Elastic IP addresses in one Traffic IP Group, with all the TMs members of this group. The outcome will be that two TMs will become active and two will become passive machines in this group.
On the failure of an active machine one of the passive will raise the dropped Elastic IP address. You could consider just having one passive machine to act as the standby for the entire cluster, allowing you to have three active machines, but this is an operational question rather than a technical one!
