From: Salau, Yemi (yemi.salau@siemens.com)
Date: Fri Aug 31 2007 - 12:52:42 ART
Your Scenario 2 looks like a loop to me, why would you want that? R1
sending to R2, and then R2 sending to R1 for same route(10.0.0.0/8)? I
still don't get it
But if you find yourself in this situation, why not increase the cost of
the route back to R1 so that R2 will only send it to R4? You can do this
easily with most Routing Protocols. If you do policy-routing, just be
careful in case you loose the link to R4, Assuming 10.0.0.0/8 can still
be reached via R1-R3, those Dscp matched packets that are still coming
from R1 will most certainly gets dropped! I would always go for the
cost/metrics/maximum-paths manipulation option.
R3 R4
| |
R1____R2
R2
sh ip route
10.0.0.0/8 R1 cost 1000
10.0.0.0/8 R4 cost 100
Many Thanks
Yemi Salau
-----Original Message-----
From: Travis Anderson [mailto:totaldrive2000@yahoo.com]
Sent: Friday, August 31, 2007 4:37 PM
To: Salau, Yemi; Cisco certification
Subject: RE: Load balancing
A lot of the lab senarios show adding multiple routes
in 1 router. A router can be congfigured with 4-6
paths with OSPF, RIP, EIGRP, and BGP.
Senario 1:Labs have this senario often(not example of
the problem)
With multiple paths in 1 router a iterative routing
loop won't occur. Both R2 and R3 will only have 1
route to reach the destination.
R2 R3
| |
|__R1__|
R1
sh ip route
10.0.0.0/8 R2
10.0.0.0/8 R3
Senario 2:
Multiple routes in R1 and R2. In this senario wouldn't
R1 and R2 load balance traffic that they had already
received from one of the destination routers? Would
manual configuration to mark the DSCP on packets from
R1 destined to R2, then R2 could policy route traffic
from routing back to R1, work?
R3 R4
| |
R1______R2
R1
sh ip route
10.0.0.0/8 R2
10.0.0.0/8 R3
R2
sh ip route
10.0.0.0/8 R1
10.0.0.0/8 R4
Here is another example
--- "Salau, Yemi" <yemi.salau@siemens.com> wrote:
> Don't quite get you clearly, but to verify,
> traceroute is a good one.
>
> To prevent Routers from loadbalancing between each
> other, isn't that
> what the maximum-paths configuration is for under
> each RP? #
>
> If you change the maximum-paths to be 1, that
> wouldn't load balance, it
> will force the RP to choose best path.
>
> Well for BGP that would be 1 by default, but I think
> for EIGRP/OSPF it's
> 4 by default. Is this what you're looking for?
>
> Also, you should be able to alter costs/metrics to
> force choosing 1
> route over the other.
>
> Many Thanks
>
> Yemi Salau
>
> -----Original Message-----
> From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of
> Travis Anderson
> Sent: Thursday, August 30, 2007 10:29 PM
> To: Cisco certification
> Subject: Load balancing
>
> GS,
>
> When load balancing, how does a person verify
> packets
> don't load balance between routers to a endpoint
> destination with any routing protocol.
>
> For instance with EIGRP the variance command is used
> on 2 routers at a remote site and the same subnet is
> entered in the routing table on both routers. R1
> receives 100 packets from a client, send 50 packets
> to
> CentralLocationR1 and 50 packets to R2. Then R2
> sends
> 25 packets to R1 and 25 packets to CentralLocationR2
> from the received 50 packets. Is there some
> mechanism
> to stop packets from being load balanced between
> each
> other? Or,is this a manual configuration and design
> question?
>
> R1
> sh ip route
> 10.0.0.0/8 R2
> 10.0.0.0/8 CentralLocationR1
>
> R2
> sh ip route
> 10.0.0.0/8 R1
> 10.0.0.0/8 CentralLocationR2
>
>
>
>
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