Load sharing question

[mike2000]

Dear All,

I would be very thankful for any useful insights anybody can provide on the following problem:

My network is setup as follows:

Internet
| s0/0 (2 Mbit l.line)
Cisco 3640---------------Cisco 2621
|s1/3 | (128K l.line)
|(128K l.line) |
| |
|s0 |
Cisco2501------------------|
s1

EIGRP is the routing protocol. My router is Cisco 2501 which is connected by 2 128Kbit/s leased lines to the 2 backbone routers. The goal is to achieve load sharing for incoming packets so that inbound traffic traverses both lines effectively giving approx. 256Kbit/s bandwidth.

To make the two routes have the same metric I have increased the delay for s0/0 on Cisco 3640 to 40000 usec.

Here is the resulting routing table entry:
---------------
Routing entry for 212.38.116.32/27
Known via "eigrp 1", distance 90, metric 21049600, type internal
Redistributing via eigrp 1
Last update from 212.38.118.1 on Serial0/0, 00:13:07 ago
Routing Descriptor Blocks:
* 212.38.116.3, from 212.38.116.3, 00:13:07 ago, via Serial1/3
Route metric is 21049600, traffic share count is 1
Total delay is 41000 microseconds, minimum bandwidth is 128 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1
212.38.118.1, from 212.38.118.1, 00:13:07 ago, via Serial0/0
Route metric is 21049600, traffic share count is 1
Total delay is 41000 microseconds, minimum bandwidth is 128 Kbit
Reliability 252/255, minimum MTU 1500 bytes
Loading 33/255, Hops 2
----------------------------

As you can see two routes appear to have equal cost and theoretically traffic should be equally split. Now in reality traffic only flows over the longer branch ??!!

Any ideas ?

Thanks in Advance

 

[wybnormal]

EIGRP will load balance two ways.. one is by packet.. one packet here, the second there adn the third back to the first path. The other is by datastreams. Datastream is the default since shuffling packets require you to turn off route caching and the router to examine each packet. This throws a heavy load on the CPU. You can balance up to 4 paths.

Take a look at the variance command which allows you to "tune" the links for load balancing. EIRGP is still noticing that one link has 1 hop and the second has 2 hops.. this is not equal load balancing, it's un-equal load balancing.. which is very achivable.

This link has all the details that you should need.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios100/eigrp/58898.htm#xtocid117936

Mike S
"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin