FA values(Forwarding address in ospf)

Hi!

The Forwarding Address is written when VRP meets the following situations:

1. OSPF is enabled on next-hop interface of ASBR;
2. the next-hop interface of ASBR is not set as passive interface;
3. the next-hop interface of ASBR is not OSPF P2P or P2MP;
4. the next-hop interface address of ASBR is within network range of OSPF protocol;
5. besides, FA is 0.0.0.0.

For learnt ase lsa, the next-hop points to adv rtr when forwarding address is 0. When forwarding address is not 0, the next-hop points to forwarding address.

Here is a great explanation with examples that you can consult for further clarification of each rule:

• https://forum.huawei.com/enterprise/en/hcie-interview-question-how-the-ospf-type-5-lsa-forwarding-address-field-affects-the-path-selection/thread/654097-861;

  
  

• https://forum.huawei.com/enterprise/en/the-impact-of-ospf-forwarding-address-on-routing/thread/614110-861.