Enabling the Forwarding of IP Source-Routed Packets

IP packets are normally routed according to the destination address they contain based on the routing table at each hop through a path. The originator or source of the source-routed packets specifies the path (the series of hops) that the packets must traverse; the source makes the routing decisions. The source can specify either of the following types of source routing:

• Strict-source routing specifies every hop that the packet must traverse. The specified path consists of adjacent hops. The source generates an Internet Control Message Protocol (ICMP) error if the exact path cannot be followed. For example, for a path going from source router A to router B to router C to router D, router A specifies a strict-source route as B, C, D.
• Loose-source routing specifies a set of hops that the packet must traverse, but not necessarily every hop in the path. That is, the specified hops do not have to be adjacent. For example, for a path going from source router A to router B to router C to router D, router A specifies a loose-source route as B, D or C, D, or B, C, D.

To enable forwarding of source-routed packets in a virtual router or VRF:

• Issue the ip source-route command in Global Configuration mode.
  host1(config)#ip source-route

  Forwarding is disabled by default in all virtual routers. Use the no version to disable forwarding of source-routed packets on the virtual router or VRF.

  If the router receives IP packets that contain either the strict source-route or the loose source-route option set in the packets and if you disable forwarding of source-routed packets by entering the no ip source-route command, the received packets are discarded. In such a scenario, the router does not process such packets when source-route forwarding is disabled.

Related Documentation

• ip source-route