Remember that loopback interfaces will show up as /32 routes in OSPF and EIGRP. Configure a summary address or range in order to reflect the proper subnet carried by the loopback interface. This is most important in LAT translation and NAT when a NAT address or LAT translation address calls for an address within the loopback's subnet. The remote router won't know about that address since only the /32 address of the loopback interface itself will be advertised. Same for PPP dialup routes apparently | IP ROUTING PROCESS Key Commands Shows and Debugs No ip route-cache will show all packets in debug Policy Routing Access-list 1 permit Route-map blah permit 10 Match ip address 1 Set default interface serial 0 Route-map blah permit 10 interface ethernet 0 ip address ip policy route-map blah Show ip cache Debug ip routing Debug ip packet Show ip route longer-prefix Additional Commands NAT Ip nat pool ccie netmask ip nat inside source list 1 pool ccie interface ethernet 0 ip nat inside ip address interface serial 0 ip nat outside access-list 1 permit Or Ip nat inside source list 1 interface s 0 overload Or Ip nat inside source list 1 pool ccie rotary Show ip nat translation Show ip nat statistics Clear ip nat trans Debug ip nat Spot The Issue In debug ip packet if seeing encapsulation failed on frame check frame map. If encapsulation failed on ethernet no arp reply so can t encaps into layer 3. Remember that loopback interfaces will show up as 32 routes in OSPF and EIGRP. Configure a summary address or range in order to reflect the proper subnet carried by the loopback interface. This is most important in LAT translation and NAT when a NAT address or LAT translation address calls for an address within the loopback s subnet. The remote router won t know about that address since only the 32 address of the loopback interface itself will be advertised. Same for PPP dialup routes apparently. .
