OSPF network command order of precedence

[kim]

Hi everyone :)

Thanks for an awesome resource!

I have a question regarding the ospf network area command. I realize that there is an order of precendence incase of overlaps. This is documented in the command reference. However reading up on ospf i came across a passage in "Routing TCP/IP Vol 1" showing this:

router ospf 8
network 172.16.0.0 0.0.255.255 area 1
network 172.16.113.0 0.0.0.255 area 0

This example, right out of the book, shows the least specific network command first. In my config i can not get the router to list the commands in that order! Almost like my 12.4 IOS orders them with the most specific first. Can you guys elaborate, maybe this is a difference in newer ios'. I know it is unimportant, but you know... Just wondering hehe.

Cheers

[Peter Paluch · Accepted solution]

Hi Kim,

I've tried two 7200 images, 12.0(32)S5 and 15.3(3)XB12. Both behave the way you have observed yourself: The network coming first in the show running-config is the most specific.

It is possible that the IOS behavior has changed, or - more probably - that the example in the book was simply written by hand and was not captured from any real router.

Best regards,
Peter

[Joseph W. Doherty · Accepted solution]

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I too have noticed current generation IOSs appear to reorder OSPF network statements, but I vaguely recall some years back, it worked as noted in the book, i.e. sequence was as entered, first match was used.