I have a problem using sortlist combined with round robin. (Bind 9.3) The scenario:
When looking up a certain domain, there are always four servers returned. Let's call them A,B,C,D. As far as i understand these are by default returned in cyclic order (round robin). The resolver is configured with sortlist to always prefer A and B. The result for this is as follows:
A, B, A, A, i.e 75/25 load balancing.
I tried to add another entry to the domain, i.e. five servers returned.
Now answers are:
A,B,A,B,B, i.e 40/60 load balancing
with three servers returned I get:
A,B,B, 33/66 load balancing
Can someone, pretty please, explain to me what is happening. Why are the answers not spread 50/50????
The only thing I can think of is that there is some kind of round robin applied to the answer on the resolver:
A,B,C,D -> A,B
D,A,B,C -> A,B
C,D,A,B -> A,B
B,C,D,A -> B,A
...and then again after the sortlist:
A,B -> A
A,B -> B
A,B -> A
B,A -> A
I am probalby totally wrong, but that is the only way I can explain this. Someone?