08-20-2009 05:47 AM - edited 03-04-2019 05:47 AM
Hi all, I have a little bit of a problem understanding the output of some ospf show commands and I was wondering if someone here can help me. Basically I don't understand why the loopback int is showing up on the output command. (see attached configuration and results of show commands)
Thank you very much in advance for your help.
Cheers!
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08-20-2009 05:55 AM
I don't understand why the loopback int is showing up on the output command.
It's the concept of the OSPF router-ID where the router selects the highest loopback interface, if available, or the highest IP address of any of the physical interfaces as router-ID.
Here is a good tutorial:
http://www.thebryantadvantage.com/CCNACertificationExamTutorialOSPFRouterIDRID.htm
08-20-2009 05:55 AM
I don't understand why the loopback int is showing up on the output command.
It's the concept of the OSPF router-ID where the router selects the highest loopback interface, if available, or the highest IP address of any of the physical interfaces as router-ID.
Here is a good tutorial:
http://www.thebryantadvantage.com/CCNACertificationExamTutorialOSPFRouterIDRID.htm
08-20-2009 05:55 AM
If you do a "show ip ospf neighbor" You should see that your loopback will be the router-id unless you specify. OSPF will always choose the loopback as such before any interface even if it has a higher 32 bit number. Thats why it shows up as an advertised router.
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