Unequal load split with static routes

Unequal load-sharing with static routes is almost impossible as there is no configuration command to assign non-default traffic share count to a static route. For example, if you configure two default routes, one pointing to a low-speed interface and another one pointing to a high-speed interface, there is no mechanism to force majority of the traffic onto the high-speed link (IOS ignores interface bandwidth when calculating load sharing ratios).

You can, howerer, use a workaround: if you configure multiple routes for the same prefix pointing to the same interface, that interface will attract proportionally more outbound traffic.

For example, let's assume you have two point-to-point serial subinterfaces, one three times as fast as the other:

interface Serial0/0/0.100 point-to-point
bandwidth 1000
ip address 172.16.1.1 255.255.255.252
!
interface Serial0/0/0.200 point-to-point
ip address 172.16.1.5 255.255.255.252
bandwidth 3000
To shift more traffic onto Serial0/0/0.200, you can create two default routes pointing to the second interface, one pointing to the interface itself, the other one to the next-hop router:

ip route 0.0.0.0 0.0.0.0 Serial0/0/0.100
ip route 0.0.0.0 0.0.0.0 Serial0/0/0.200
ip route 0.0.0.0 0.0.0.0 172.16.1.6
This setup will give you a 1:2 sharing ratio. To shift even more traffic to the higher-speed interface, one has to get more creative

Create a bogus host route for a bogus next-hop pointing to the actual next-hop router (and make sure you don't advertise the bogus route into your routing protocols).
Configure yet another static route pointing to the bogus next-hop. Due to recursive lookup done by Cisco IOS, the bogus next-hop will be resolved into the actual next-hop IP address.
In our example, you could use:

ip route 10.255.255.1 255.255.255.255 172.16.1.6
ip route 0.0.0.0 0.0.0.0 10.255.255.1
The results are as expected: the traffic split is the desired 1:3 ratio

a1#show ip route 0.0.0.0 0.0.0.0
Routing entry for 0.0.0.0 0.0.0.0, supernet
Known via "static", distance 1, metric 0 (connected), candidate default path
Routing Descriptor Blocks:
172.16.1.6
Route metric is 0, traffic share count is 1
10.255.255.1
Route metric is 0, traffic share count is 1
* directly connected, via Serial0/0/0.100
Route metric is 0, traffic share count is 1
directly connected, via Serial0/0/0.200
Route metric is 0, traffic share count is 1

a1#show ip cef 0.0.0.0 0.0.0.0 internal
0.0.0.0/0, version 43, epoch 0, attached, per-destination sharing
0 packets, 0 bytes
via 172.16.1.6, 0 dependencies, recursive
traffic share 1
valid adjacency
via 10.255.255.1, 0 dependencies, recursive
traffic share 1
valid adjacency
via Serial0/0/0.100, 0 dependencies
traffic share 1
valid adjacency
via Serial0/0/0.200, 0 dependencies
traffic share 1
valid adjacency

0 packets, 0 bytes switched through the prefix
tmstats: external 0 packets, 0 bytes
internal 0 packets, 0 bytes
Load distribution: 0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3 (refcount 1)

Hash OK Interface Address Packets
1 Y Serial0/0/0.200 point2point 0
2 Y Serial0/0/0.200 point2point 0
3 Y Serial0/0/0.100 point2point 0
4 Y Serial0/0/0.200 point2point 0
5 Y Serial0/0/0.200 point2point 0
6 Y Serial0/0/0.200 point2point 0
7 Y Serial0/0/0.100 point2point 0
8 Y Serial0/0/0.200 point2point 0
9 Y Serial0/0/0.200 point2point 0
10 Y Serial0/0/0.200 point2point 0
11 Y Serial0/0/0.100 point2point 0
12 Y Serial0/0/0.200 point2point 0
13 Y Serial0/0/0.200 point2point 0
14 Y Serial0/0/0.200 point2point 0
15 Y Serial0/0/0.100 point2point 0
16 Y Serial0/0/0.200 point2point 0


Read more: http://blog.ioshints.info/2007/02/unequal-load-split-with-static-routes.html#ixzz0qTjNprvX