02-11-2009, 02:35 PM
RTA e0 has nothing to do with RIP updates to RTC. RTA e0 is a LAN interface and is not connected to any other router and RIP can be disabled on that interface. RTA uses s0 to advertise routes to neighboring router RTB, including the network on e0. If the passive-interface command was used on the RTA s0 interface, then you would be correct. There's no passive-interface command on s0, so RTA will advertise routes out s0 to RTB s0/0. RTB will advertise those same routes out s0/1 to RTC since it too has no passive-interface command set. RTC will receive that update via its s1 interface since the passive-interface command still allows updates to be received. So, there's the path from the e0 network on RTA getting to RTC's routing table.