I have a question about ticket #4 for CCIE R&S v5 Troubleshooting Lab 2. One of the solutions is that- R5 has no usable address to set as the Forwarding Address despite having 2 interfaces in ospf process 1 for area 34. is it required that the forwarding address not have any neighbors or be a loopback address? any assistance and/or links to reference materials would be greatly appreciated.
The documenation i found published by cisco provides the following criteria for selecting a forwarding address on the ASBR whcih appears to indicate is is possible to use the Ip from a physical interface as the forwarding address
Forwarding address is selected on ASBR using the following rules:
- If there is a loopback configured in the area then IP address of loopback is selected as forwarding address.
- If first condition is not met then IP address of first interface on the OSPF interface list is selected as forwarding address. You can see OSPF interface list by using "show ip ospf interface brief" command. The interface on top will be the last interface which was attached to OSPF.