From: ccie2be (ccie2be@nyc.rr.com)
Date: Wed Jul 07 2004 - 18:48:40 GMT-3
Hi Brian,
Thanks for thinking about this and getting back to me with your thoughts.
Unfortunately, I'm not able to try this, but based on what I know, I don't
think this would work.
Here's my thinking. Please let me know if you agree or not with this
reasoning.
As you say, eigrp, by default, considers 2 parameters in it's metric
computation: delay and (min) bandwidth.
By configuring variance on R2 and R3 such that twice as much traffic flows
over the 2mb link as the 1mb link for traffic going from R3 to R2, I've
taken care of the first objective.
You're right that I can change the delay on the 1mb link on R3 and that will
affect the unequal cost load balancing for traffic from R3 to R1, but won't
that also screw up the ratio of traffic flowing over both links from R3 to
R2?
What I want to do is make sure the ratio of traffic flowing from R3 is 2:1
regardless of whether that traffic is destine for R2 or R1. Now since the
64k link between R2 and R1 is the minimun bandwidth in the path from R3 to
R1, I think I need to figure out some way to take that link out of the
equation.
Suppose, for example, Eigrp thought the bandwidth of the 64k link was 2mb.
In this case, R3 wouldn't be influenced by bandwidth of the link between R2
and R1; and thus would unequal load balance based on just the metrics of the
two links between R3 and R2. Do you agree?
If so, then the question becomes: Should the bandwidth be changed on R1 or
R2?
What do you think?
Thanks, Tim
----- Original Message -----
From: "Jensen, Brian D." <bdjensen@eschelon.com>
To: "'ccie2be'" <ccie2be@nyc.rr.com>; "Group Study" <ccielab@groupstudy.com>
Sent: Wednesday, July 07, 2004 5:10 PM
Subject: RE: Eigrp unequal load balancing problem
> Hi Tim,
>
> The Cisco recommended way to change the metrics for the two links is to
> alter the delay on one of them. I am guessing that both of your links
> between R3 and R2 have the same delay. Increase the delay on the 1mb link
on
> R3's side, and then you should see the metric change. If you are running
the
> default eigrp config, then its only bandwidth and delay for the
computation.
> If you enable all of the k-values, then its possible that the metrics
would
> already be different, as then load, reliability and mtu are included in
the
> metrics.
>
> HTH,
>
> Brian
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> ccie2be
> Sent: Wednesday, July 07, 2004 2:02 PM
> To: Group Study
> Subject: Eigrp unequal load balancing problem
>
>
> Hi guys,
>
> Here's the scenario:
>
>
> 2 mbps
> R1 -----64k ----- R2 ========= R3
> 1 mbps
>
>
> All routers are running Eigrp. R2 and R3 have unequal load balancing
> configured.
>
> Traffic between R2's lo0 and R3's lo0 unequal load balances perfectly.
> However, traffic between R1's lo0 and R3's lo0 don't
> unequal load balance. In this case, traffic is balanced equally across the
2
> links between R2 and R3.
>
> The reason for this is that from R3's point of view, the 2 paths to R1
have
> an
> equal cost, not an unequal cost because the metric Eigrp uses is based on
> the
> minimum bandwidth link from source to destination which in this case is
the
> 64k link between R2 and R1.
>
> Is it possible to reconfigure the network so that R3 sees the 2 paths to
R1
> as
> having different costs?
>
> And, if so, how can that be done?
>
>
> TIA, Tim
>
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