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kim Beginner
Beginner

OSPF network command order of precedence

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

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Accepted Solutions
Hall of Fame Cisco Employee

Hi Kim,I've tried two 7200

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

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VIP Expert

DisclaimerThe Author of this

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

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.

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2 REPLIES 2
Hall of Fame Cisco Employee

Hi Kim,I've tried two 7200

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

View solution in original post

VIP Expert

DisclaimerThe Author of this

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

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.

View solution in original post

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