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Hall of Fame Super Gold

OSPF 'topology priority' ?

Does anybody knows what is this used for?

TMT-HE-GW(config)#router ospf 1

TMT-HE-GW(config-router)#p?

Router configuration commands:

  passive-interface      Suppress routing updates on an interface

  prefix-suppression     OSPF prefix suppression

  priority               OSPF topology priority

TMT-HE-GW(config-router)#priority ?

  <0-127>  OSPF topology priority

Totally undocumented, started appearing in 15.1

  • WAN Routing and Switching
7 REPLIES
Super Bronze

OSPF topology priority ?

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

As a guess, something like AD for multiple OSPF processes on the same device.

Cisco Employee

OSPF topology priority ?

Hi Joseph,

Hey, you've become all purple! Congratulations, it's more than well earned and deserved!

Hmmm, I am also making a guess but I don't think this has to do with AD. Among others, the range of permitted values does not fit: it's between 0 and 127, while AD is usually configurable between 1 and 255. The keyword established for AD is distance and I don't think it would get changed.

My personal opinion: This priority may be related to the scheduling of SPF runs between different topologies. In case of a need to run the SPF for multiple topologies, they will be scheduled according to their priority, highest-priority-first, thereby making convergence in selected topologies more expedite.

Paolo, does that command accept any other parameter besides the numerical priority?

In any case, we're just guessing. I hope Edison and other experts from Cisco will join and provide an authoritative information.

Best regards,

Peter

Super Bronze

OSPF topology priority ?

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

Peter, thank you for the congrats.  (If you're wondering how you jump from gold to purple, a couple years ago when Cisco did maintenance on this site they spawned off a new account.  My original account was close to purple.  I recently asked Dan to merge the original and spawned accounts since I've resumed posting.)

Sorry, I wasn't clear when I wrote "something like AD".  What I had in mind, this value might allow you to take one OSPF process's routes in preference to another OSPF process since they would both have the same AD and you can have multiple OSPF processes on the same platform.  I.e. this isn't directly related to AD except as an additional "tie breaker".  Again, though, just a guess.

Your guess, though, is interesting too.

Paolo, anything similar for EIGRP?

Hall of Fame Super Gold

OSPF topology priority ?

I have a feeling, that if one was to read the IETF working group "works", would find what is that. But, I'm just too lazy /

Cisco Employee

OSPF topology priority ?

Paolo,

As a matter of fact I went over the RFC 4915 (MTR for OSPF) but did not find any mention of a priority of any kind.

Once again, is the priority value the only valid argument for this command?

Best regards,

Peter

New Member

It is indeed used for MTR

It is indeed used for MTR OSPF

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mtr/configuration/15-s/mtr-15-s-book/ospf-support-mtr.html

Hall of Fame Super Gold

OSPF 'topology priority' ?

Yes.

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