We've recently changed our proxy topology from in-line transparent now to WCCP. Our WCCP router ACL forwards all port 80 and 443 traffic to the proxy. The proxy has a number of static bypass entries for both source and destination hosts and networks. We've found that for any session that has a static bypass, the proxy only sees client-initiated packets. This is because for a bypassed session the proxy maintains the client IP address as the source IP when sending the packet to the OCS. The WCCP router simply sends reply packets for these sessions straight to the client, rather than back to the proxy.
That wouldn't necessarily be a problem, but the proxy also sometimes modifies the packets of bypassed sessions by changing payload sizes, thus modifying TCP sequence numbers. Since the client and server are now out of sequence, this causes the session to slow and usually fail.
I don't know if this reflects some problem with router settings or proxy settings. How do we get the router to send the packets back to the proxy? How do we get the proxy to stop modifying packets in bypassed sessions? The only solution we can think of is to move the entire static bypass list to the router, but since that's not mentioned in any documentation as a recommendation or requirement for WCCP, we're unsure what the right course is.
Is WCCP and static bypass fundamentally incompatible? Or is there some configuration change required?
Thanks for any input.
- D