Question : Riverbed with Cisco GRE Tunnel

Are the Riverbed 1050L WAN Optimization devices able to optimize Cisco GRE Tunnel traffic?  Since the GRE tunnels mask the routing bits, will the Riverbed be able to understand that portion of the packet?

Answer : Riverbed with Cisco GRE Tunnel

unfortunately, according to Riverbed, as one of the requirements to "ensure that the WAN optimization solution can be deployed easily and transparently in to the enterprise network", "the solution must NOT use tunnels."

FYI

Technical Requirements for WAN Optimization RFP
http://www.riverbed.com/docs/WhitePaper-Riverbed-TechRequirements-RFP.pdf

hope it helps,
bbao