Internet Engineering Task Force (ietf) Extending Icmp for Interface and Next-hop Identification

This memo defines ICMP extensions, using ICMP multi-part messages, through which a router or host can explicitly identify the interface upon which an undeliverable datagram anrrived. The incoming interface can be identified by ifIndex, name, and/or address, as already used in MIBs and by OSPF. The extensions defined herein are particularly useful when troubleshooting networks with unnumbered interfaces, parallel interfaces and/or asymmetric routing.