From: Peter van Oene (pvo@usermail.com)
Date: Wed Oct 16 2002 - 15:23:09 GMT-3
In many networks, particularly ISP networks, the topologies are not such
that there is lot of metric parallelism in paths and equal cost load
balancing alone does not effectively utilize a given
topology. Furthermore, it may not be that you want to purely load balance
traffic, but you might want to selectively map certain traffic to certain
links and other traffic to other links. Doing this with metric
manipulation is not possible, and policy routing needs to be done per
router along a given path and really has some provisioning drawbacks, not
too mention may seriously degrade forwarding performance on some platforms.
These types of issues, be they QoS centric or simply a desire to
intelligently engineer traffic flows over a given topology, are some of the
reasons why MPLS finds use in many networks. Most people think of MPLS
these days as a VPN enabler, but it certainly has other uses.
At 02:16 PM 10/16/2002 -0400, Larson, Chris wrote:
>Ahh well. Now your talking about real world stuff. In that case I would
>not want to do policy routing either.
>
>Just out of curiosity, in the real world why would you want to take a
>certain path on links that could LB anyway?
>-----Original Message----- From: Peter van Oene
>[SMTP:pvo@usermail.com] Sent: Wednesday, October 16, 2002 2:09
>PM To: Larson, Chris; 'Volkov, Dmitry (Toronto - BCE)'; Dave
>Cooper Cc: CCIE Subject: RE: OSPF route manipulation
>
>I suppose you could butcher things that way. My point of view it
>skewed toward reality :-) Policy routing per destination on your GSR is
>not really a good thing.
>
>At 01:37 PM 10/16/2002 -0400, Larson, Chris wrote: >Without getting into
>it to much, can't you just use a route-map on the >interfaces of R4 to
>define the wieght of the routes? Or policy routing that >sets the next
>hop based on destination? > > > -----Original Message----- > > From:
>Volkov, Dmitry (Toronto - BCE) [SMTP:dmitry_volkov@ca.ml.com] > > Sent:
>Wednesday, October 16, 2002 1:05 PM > > To: Dave Cooper > >
>Cc: 'Peter van Oene'; CCIE > > Subject: RE: OSPF route
>manipulation > > > > I guess You can use distance : > >
><http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ip>http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ip
> > > _r > > /iprprt2/1rdindep.htm#xtocid2 > > > > > >
>Dmitry > > > > > -----Original Message----- > > > From: Peter van Oene
>[<mailto:pvo@usermail.com>mailto:pvo@usermail.com] > > > Sent: Wednesday,
>October 16, 2002 12:32 PM > > > To: Dave Cooper; CCIE > > > Subject: Re:
>OSPF route manipulation > > > > > > > > > Can't do it. This type of
>granular traffic engineering is one of the > > > things MPLS-TE is useful
>for. Metric based TE is topology > > > centric and > > > fixed for all
>destinations over a given topology. The > > > topology itself > > >
>cannot be modified on a per destination basis. > > > > > > At 06:14 AM
>10/16/2002 -0700, Dave Cooper wrote: > > > >Hi > > > > > > > >Four
>routers in a diamond
>shape > > > > > > > > |----r2----| > > > >r1 r4 > > > >
>|----r3----| > > > > > > > >All are in area 1. All interfaces serial
>p-2-p > > > > > > > >R1 is advertising 2 routes x.x.0.0 &
>y.y.0.0 > > > >R4 has 2 equal paths for each (via r2 & via
>r3) > > > > > > > >How can I force r4 to "prefer" r2 for x.x.0.0 and
>r3 > > > >for y.y.0.0 > > > >In case prefered path is not there, use the
>other > > > >path. > > > > > > > >I tried using
>cost/bandwidth/distribute-list. But they > > > >can't distinguish x from
>y and change metric > > > >accordingly. > > > > > > > >Is this possible
>? > > > > > > > >Thanks > > > >Dave > > > >
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