On Friday, August 12, 2011 18:02:20 Antonio Quartulli wrote:

In your topology you have three nodes: A, B and C. A and C are GWs. A is
the current best GW for B and B got an IP from the DHCP server running on
A. Then the link A <--> B becomes worse than B <--> C. At this point
Batman-adv will drop a DHCP unicast renewal request directed to A

if and only if TQ(C) - TQ(A) > 50

Be aware that only happens if you use the git repository. The "DHCP request 
drop" feature was not released yet.

What version are you using ?

Cheers,
Marek