Troubleshooting

From Brian Valentine CCIE What you could do is on R1,

conf t

no ip cef inter fas0/1 no ip route-cache

access-list 101 permit icmp any any end

debug ip packet detail 101 term mon

Then attempt your pings again. If the router is receiving and sending pings, it will show you in the output of the debug. If the router is sending icmp echoes toward the host, but not getting any icmp echo replies back, I would assume some sort of host-based firwall is blocking them.

Turning off cef and route-caching forces the router to use the RIB (Routing Information Base, aka. the route table) for every packet instead of the FIB (Forwarding Information Base). In effect, every packet will hit the router's cpu to figure out where it should be forwarded. This is necessary in order for the router to "see" the ping packets as matching the ACL in order to display them in the debug output. Otherwise, the router will only display packets that it has to actually process, which include packets directed toward (or sources from) itself.