Routing

Hi, all!

I have a question about ospf. Following is the topology. All the link are fastethernet.

If the link between R2 and R4 down. Does R1 ping R5 successful and why?

ThankS!

Hello,

The answer is "it depends":

1/ with JUNOS version <7.2 and without virtual link between R2 and R3 - NO. 

2/ with  JUNOS version 7.2 and newer, YES 

3/ with virtual link between R2 and R3 YES

Google "junos no-active-backbone" for more information

HTH

Rgds

Alex 

Based on your diagram, if the link is lost between R2 and R4 only, your traffic would flow via R3 to R4 (the longest path to R5)

If you look at the current OSPF databse in R1, you should see that R5' loopback IP (172.16.1.5) being installed into database as Type3-LSA from ABR (R2 and R3).

If the link is disappear and become unreachable, the ABR must flush the LSA from domain by setting it to Maxage (3600 seconds) and reflood.

Is there any problem else that you facing?

Hi, Thanks

can i disable ospf active backbone detection on ABR? I tried, but there's no the command "no-active-bacebone"

Thanks!

This command is hidden, you have to type it in full.

set protocols ospf no-active-backbone

 HTH

Rgds

Alex

Hi, Thank you guys!