From: Tim Fletcher (groupstudy@fletchmail.net)
Date: Thu Jul 08 2004 - 12:07:46 GMT-3
Brian,
Can you post the bandwidth and delay parameters from a "sh int" for each of
the interfaces involved.
-Tim Fletcher
At 11:52 PM 7/7/2004, Jensen, Brian D. wrote:
>Hi Tim,
>
>My curiosity was piqued, so I set this up in the lab:
>
>R1 Lo = 10.1.1.1
>R3 Lo = 10.3.3.3
>R2 Lo = 10.2.2.2
>Topology is same as original diagram, R1----R2===R3. Between R2 and R3,
>band on s0/0 is set to 2mb, and s0/1 is set to 1mb on both sides.
>
>Here are the routes from R3's perspective:
>D 10.2.2.0/24 [90/7519] via 10.100.1.1, 00:00:02, Serial0/0
> [90/12539] via 10.200.1.1, 00:00:02, Serial0/1
>D 10.1.1.0/24 [90/183771] via 10.200.1.1, 00:00:02, Serial0/1
> [90/183771] via 10.100.1.1, 00:00:02, Serial0/0
>
>Here are the routes from R2's perspective:
>D 10.1.1.0/24 [90/181771] via 10.11.0.1, 00:00:02, Serial1/1
>D 10.3.3.0/24 [90/7029] via 10.100.1.2, 00:00:02, Serial0/0
> [90/12049] via 10.200.1.2, 00:00:02, Serial0/1
>
>
>Its the strangest thing, I get load balancing between R2 and R3 in the ratio
>of 2:1, but if the traffic goes from R1 to R3, then there is no load
>balancing. I have tried using the variance, and even "traffic bal" under
>eigrp on both sides, and the traffic still prefers the hi bw link, or s0/0.
>These results are not what I expected to see. Now I too am asking, why is
>this so?
>
>Thanks,
>Brian
>
> > -----Original Message-----
> > From: nobody@groupstudy.com [SMTP:nobody@groupstudy.com] On Behalf Of Tim
> > Fletcher
> > Sent: Wednesday, July 07, 2004 10:01 PM
> > To: ccie2be; Sergio Jimenez Arguedas; ccielab@groupstudy.com
> > Subject: Re: Eigrp unequal load balancing problem
> >
> > At 08:33 PM 7/6/2004, ccie2be wrote:
> > >OK, guys. You're not getting it, so I'll give you a hint.
> > >
> > >The problem is that from R3's point of view, the 2 paths to R1 are equal
> > >cost. This is because when Eigrp figures out the cost to a destination,
> > it
> > >using the lowest bandwidth link anywhere along the path to the
> > destination.
> > >Since the path to R1's lo0 includes a single 64k link between R2 and R1,
> > >from R3's point of view both paths to R1 are equal.
> >
> > That's not entirely true. EIGRP does use the lowest bandwidth link in the
> > path, but it also uses the cumulative delay. So you will see a larger
> > difference in the metrics to reach R2 than the metrics to reach R1.
> >
> > From R3's perspective, the two paths to R2 are going to have different
> > bandwidth and delay values, but the two paths to R1 are only going to have
> > a difference in the delay value. The difference will also be smaller
> > because both paths will include the 64K link which will have a higher
> > delay than either of the other links. So you should see a difference in
> > the metrics to R1, but it will be much smaller.
> >
> >
> > >That, unfortunately, is as much as I know. What I don't know is how to
> > >overcome this problem such that R3 unequal load balances traffic to R1
> > just
> > >llike it does with traffic to R2.
> >
> > How about changing the EIGRP k values to achieve what you're after. One
> > possibility is to set them to only use delay, then set the delay very low
> > on the 64K link from R2 to R1. This should give you pretty close to the
> > same distribution.
> >
> >
> >
> > >----- Original Message -----
> > >From: "Sergio Jimenez Arguedas" <sejimenez@its.co.cr>
> > >To: <ccielab@groupstudy.com>
> > >Sent: Thursday, July 22, 2004 8:14 PM
> > >Subject: RV: Eigrp unequal load balancing problem
> > >
> > >
> > >> Hi,
> > >>
> > >> I think traffic shara balanced is the option!!!
> > >>
> > >>
> > >http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/f
> > ipr
> > >> rp_r/1rfeigrp.htm#wp1024898
> > >>
> > >>
> > >> Rgds,
> > >>
> > >>
> > >> Sergio
> > >>
> > >>
> > >> -----Mensaje original-----
> > >> De: nobody@groupstudy.com [mailto:nobody@groupstudy.com]En nombre de
> > >> ccie2be
> > >> Enviado el: martes, 06 de julio de 2004 17:44
> > >> Para: tycampbell@comcast.net; Group Study
> > >> Asunto: Re: Eigrp unequal load balancing problem
> > >>
> > >>
> > >> Nope, not the answer.
> > >>
> > >> Variance is already configured and unequal load balancing already works
> > >> between R2 and R3.
> > >>
> > >> The problem is that while unequal load balancing works between R2 & R3,
> > >> unequal load balancing *doesn't* work between
> > >>
> > >> R1 and R3.
> > >>
> > >> Why?
> > >>
> > >> And, what is the solution?
> > >>
> > >>
> > >> ----- Original Message -----
> > >> From: <tycampbell@comcast.net>
> > >> To: "ccie2be" <ccie2be@nyc.rr.com>; "Group Study"
> > <ccielab@groupstudy.com>
> > >> Sent: Tuesday, July 06, 2004 7:06 PM
> > >> Subject: Re: Eigrp unequal load balancing problem
> > >>
> > >>
> > >> > I think variance may be the answer you are looking for
> > >> >
> > >> > variance of 2 should do it for this scenario
> > >> >
> > >> >
> > >> > > 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.
> > >> > >
> > >> > > What the best way to have twice as much traffic going over the 2
> > mbps
> > >> link
> > >> > > from R3 to R2 as the 1 mbps link between those 2 routers?
> > >> > >
> > >> > >
> > >> > > TIA, Tim
> > >> > >
> > >> > >
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