From: Clark, Jeffrey (Jeffrey.Clark@nasdaq.com)
Date: Thu Nov 06 2003 - 11:41:49 GMT-3
Last week I actually received a Cisco AS best practices document from our AS guy. The doc isn't complete yet they are still working on it, but it does say that if you change the auto-cost reference bandwidth on one router it should be changed on all routers in the domain. Their suggestion is actually to change it to the highest bandwidth link in the domain and to let OSPF determine the best paths.
It also say that it can be done by area, since generally the highest bandwidth links are in the core and sometimes more a granular reference point is needed if there are some big fat pipes in the core and some really skinny ones in another area. But care should be done when doing this, since links do connect the area together the reference needs to be consistent to not cause sub-optimal routing.
-----Original Message-----
From: Leigh Bichard [mailto:leigh@clara.co.uk]
Sent: Wednesday, November 05, 2003 1:24 PM
To: Rob Laidlaw
Cc: ccielab@groupstudy.com
Subject: Re: OSPF auto-cost
Rob
Makes sense.
Thanks
Rob Laidlaw writes:
> Good rule of thumb is yes, so everyone is apple to apple. If you have two
> paths, and one guy is using a reference bandwidth of 1gig and the other is
> default, 100m, then the cost will be advertised different in the LSA's. Now
> lets assume that the best path is actually through the box with the
> auto-cost changed because he might have a oc-3 interface as opposed to the
> guy whose still at the default config with his 100 meg Ethernet. if you
> change the cost, on one but not the other, but router with the default
> config will advertise a cost of 1 with his lsa, and the modified router will
> advertise a cost of 6 or 7.
>
> Good rule of thumb is if you change one, change them all.
>
> -Rob
> ----- Original Message -----
> From: "Leigh Bichard" <leigh@clara.co.uk>
> To: <ccielab@groupstudy.com>
> Sent: Wednesday, November 05, 2003 11:31 AM
> Subject: OSPF auto-cost
>
>
>> I can't find a definitive but does auto-cost, if changed, need to be
> applied
>> to all OSPF routers in ALL areas?
>>
>> Thanks
>>
>> _______________________________________________________________________
>> Please help support GroupStudy by purchasing your study materials from:
>> http://shop.groupstudy.com
>>
>> Subscription information may be found at:
>> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Fri Dec 12 2003 - 12:29:09 GMT-3