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load balance in eigrp question

Now, I meet some load balance questions in eigrp:

1)There are 2 routers from NetA to NetB in Eigrp, and one via Ethernet0 and the other via Serial0.These 2 routers deploy load balance. But now the load balance don't work, even if I change router metric the Serial link less than the router metric via Ethernet0 by changing link bandwith and delay, the data only go out form Ethernet0 router link to destination.(I'm sure the Eigrp variance is configured properly)

2)When I test load balance via record Ping from NetA to NetB, the load balance works normally. But I test via FTP(FTP server in NetA and client in NetB), the load balance works unnormal.It only go from one router link.Is it because that the FTP flow is TCP packet, and the router and Layer3 Switch remember the FTP flow route information ?


Re: load balance in eigrp question


There is fast switching (per-destination switching) enabled on the router interfaces. That's why by default the router does per-destination load-balancing. If you have both the routes in the routers routing table ( Check with "show version") and it is sending traffic via only one link, it is that the router is doing per destination load-balancing. You can change this default behaviour by using " no ip route-cache " under the router interfaces. This will change the load-balancing to per-packet.

Also have you checked doing FTP by multiple source clients on FTP clients. It should send the session on both the links in case of multiple clients.

HTH, Please rate if it does.

-amit singh

Community Member

Re: load balance in eigrp question

Tanks for amit-singh.I will test today. But for Question1,I'm confused.For example,now I enable backup interface for serial link.If the serial link traffic is saturated, its backup interface--ethernet link will go up and now there are 2 router links and load balance.Before the ethernet link goes up, the FTP flow have to go from serial link. But once the ethernet link goes up, the all data flow immediately change to going from ethernet link, even if the serial router link has less metric. why ?


Re: load balance in eigrp question

Can you confirmt the metric of the serial link is actually lower than the Ethernet ? Did you try to configure the bandwidth of Ethernet to lower than serial ?

Check below :

Please provide the "sh ip route" if the problem still exists.

Hope this helps.


Re: load balance in eigrp question

Actually, a show ip eigrp topo for one specific route would be really helpful. We only load share between S' and FS'. If the RD==FD, the it's not an FS, and we won't load share, even with variance configured.



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