Hi Dieter,
Are you referring to the WCCP GRE encapsulation between the router and WAE? If so, the GRE packets are use the IP address of the WAE and the WCCP router ID of the router. The WCCP router ID is chosen the same way a OSPF/BGP router ID is chosen - the IP address of the loopback interface or the highest IP address of an administratively enabled non-loopback interface (when a loopback interface isn't configured). You can see the WCCP router ID in the output of the command sh ip wccp on the router. For example:
AST6-DCN-RTR-2#sh ip wccp
Global WCCP information:
Router information:
Router Identifier: 10.88.81.99
Protocol Version: 2.0
Service Identifier: 61
Number of Service Group Clients: 1
Number of Service Group Routers: 1
Total Packets s/w Redirected: 167
Process: 0
CEF: 167
Service mode: Open
Service Access-list: -none-
Total Packets Dropped Closed: 0
Redirect Access-list: -none-
Total Packets Denied Redirect: 0
Total Packets Unassigned: 60
Group Access-list: -none-
Total Messages Denied to Group: 0
Total Authentication failures: 0
Total GRE Bypassed Packets Received: 0
Service Identifier: 62
Number of Service Group Clients: 1
Number of Service Group Routers: 1
Total Packets s/w Redirected: 0
Process: 0
CEF: 0
Service mode: Open
Service Access-list: -none-
Total Packets Dropped Closed: 0
Redirect Access-list: -none-
Total Packets Denied Redirect: 0
Total Packets Unassigned: 0
Group Access-list: -none-
Total Messages Denied to Group: 0
Total Authentication failures: 0
Total GRE Bypassed Packets Received: 0
AST6-DCN-RTR-2#
Regards,
Zach
