Re: IGP metrics on WAN links

[Me <smentzer () mentzer org>]

Since both isis and ospf support a large range of metrics nowadays, the
actual mileage itself is an option for the metric too.  For example,
before isis wide metrics, a route with fiber mileage of 1000 might be
given an isis metric of 16(using the method Sush mentioned to get the
metric within the isis metric range of 0-63, so 1000/64 = 15.625, round
up to 16), but now with wide metrics, the actual mileage can be used.

Using the wide metrics also helps reduce/eliminate the equal cost paths
that used to crop up in large networks with a limited metric range.




and actual mileage of 1000On Fri, 19 Jul 2002, Sush Bhattarai wrote:

> Date: Fri, 19 Jul 2002 14:25:16 -0400
> From: Sush Bhattarai <netnews () sush org>
> To: nanog () merit edu, Tom Holbrook <tomhol () corp earthlink net>
> Subject: Re: IGP metrics on WAN links
>
>
> Think most ISPs use actual fiber miles (with an arithmetic factor to get to
> a certain range of course) as the means for the value of IGP metrics... of
> course there are always some "twinking" done regularly to give higher
> priorities to the higher bandwidth, link condition etc.
>
> Sush
>
>
> ----- Original Message -----
> From: "Tom Holbrook" <tomhol () corp earthlink net>
> To: <nanog () merit edu>
> Sent: Friday, July 19, 2002 12:27 PM
> Subject: IGP metrics on WAN links
>
>
> > Just curious as to what people are using for metrics in their IGP and what
> > their reasons are; bandwidth? geographical distance? latency? etc...
> >
> > Thanks
> > -Tom
> >
> > __________________
> > Tom Holbrook
> > Sr. Network Engineer
> > Atlanta
> > Earthlink

-sean
Spoon!