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Source-hash limitations for multiple servers on a subnet
As I understand the source hash option, it will redirect the packet to
one of a set of IPs based on a hash of the source address.
This is dandy in a 'sticky load balancing' situation, when you have a
power of two number of servers, and they are all running.
However, if I had 4 destination IPs
and I was load balancing across the set as 188.8.131.52/30, what could I do
if 184.108.40.206 was no longer available? As I understand it, all I could do
would be to load balance across 220.127.116.11/31 at best?
Similarly, if I had 3 servers, I could only balance across two.
This seems a bit limiting. Would it not be more appropriate to use the
source address to work out which of the listed IP address (after
expanding CIDR notation) should be chosen? That way no "memory" of the
previous choice would be required. Admittedly, if the number of
destinations in the rule changed, connections would be routed
differently, but that would seem to be the case anyway.