load balance using EIGRP

[morriszhu]

hello, there are 2 routers connecting to one external application server through 2 leased lines, between the server and the 2 routers, there are mix of other routers also. when we set the EIGRP on the 2 routers, even with Variance 2, 60 or 128, we could hardly see the load balance routes on the external connections - in reverse, there appeared the load balance routes on the internal connections (only for equal paths). So can we set the load balance on the 2 routers (they are back to back connected through fast ethernet ports) without considering how complex the router mix between these 2 routers and the server.

That means when the data go out to the server through these 2 routers, the traffic will be balance on these 2 routers based on the line speed / load of the 2 leased lines without considering the other router mix.

In addition, can this load balance only affect the external 2 leased line connection? not affect the internal connections between these 2 routers and internal users. thanks!

[rsissons]

By default, the router will always attempt to load share over, up to 4, equal cost paths. However, this will be on a session level, rather than on a per packet basis so you will not actually see equal utilisation, especially if there are only a few sessions.

It is possible to force load sharing on a per packet basis by disabling fast switching on the interfaces, however this is not recommended as it can severely impact the performance of the router.

It is definately NOT recommended when using the variance operand with EIGRP to force loadsharing over unequal cost paths, since packets would then arrive out of order and require resequencing at the destination which would also impact performance.

[morriszhu]

thanks for the advice, but when the 2 lines - one 1024k, another 2048k, the traffic will go through 2048k always even it is high loaded, while the 1024k is empty. how to utilize the lines effectively? thanks!