IPv6 uRPF operation

Figure 149 shows how IPv6 uRPF works.

1. IPv6 uRPF checks whether the received packet carries a multicast destination address:

   • If yes, IPv6 uRPF permits the packet.

   • If no, IPv6 uRPF proceeds to step 2.

2. IPv6 uRPF checks whether the source address matches a unicast route:

   • If yes, IPv6 uRPF proceeds to step 3.

   • If no, IPv6 uRPF discards the packet. A non-unicast source address matches a non-unicast route.

3. IPv6 uRPF checks whether the matching route is to the host itself:

   • If yes, the output interface of the matching route is an InLoop interface. IPv6 uRPF checks whether the receiving interface of the packet is an InLoop interface. If yes, IPv6 uRPF permits the packet. If no, IPv6 uRPF discards the packet. If the source address is a link-local address and is the receiving interface address, the packet is discarded.

   • If no, IPv6 uRPF proceeds to step 4.

4. IPv6 uRPF checks whether the receiving interface matches the output interface of the matching FIB entry:

   • If yes, IPv6 uRPF proceeds to step 5.

   • If no, IPv6 uRPF checks whether the check mode is loose. If yes, IPv6 uRPF proceeds to step 5. If no, IPv6 uRPF discards the packet.

5. IPv6 uRPF checks whether the matching route is a default route:

   • If yes, IPv6 uRPF checks whether the allow-default-route keyword is configured to allow using the default route. If yes, the packet is forwarded. If no, the packet is discarded.

   • If no, IPv6 uRPF forwards the packet.