I am only seeing this with the B systems at the moment.. and I am
trying to figure out how I should 'fix' my firewall or backbone DNS
server to deal with it.

Our campus DNS servers will 'proxy' a request to the backbone DNS
servers and when it talks to the B servers, we get requests back from
different IP address from what we sent to (thus our firewall drops it
as a bad session). > > > >

This really picked up on Saturday when pretty much every send to the server got 1 to 2 other returns from b1.ip4.int,
b2.ip4.int etc.

The only other servers that the firewall seems to be dropping are some
'questionable' ones in Romania that showed up over the weekend.

Stephen J Smoogen. -- CSIRT/Linux System Administrator
How far that little candle throws his beams! So shines a good deed
in a naughty world. = Shakespeare. "The Merchant of Venice"