how I do load balancing in Cisco 3725

[hungnt]

Hi all !

I have a network topo described below:

- LAN network connected to SW3550.

- SW3550 connected to Cisco3735 by ethernet.

- Cisco3725 connected to 2 external ADSL_MODEM to 2 different IPS for backup and loadbalancing purpose.

links and routing protocol:

1. C3725 <--> ADSL1 : FastEthernet. Static routing

2. C3725 <--> ADSL2 : FastEthernet. Static routing

3. ADSL1 <--> IPS1 : ADSL. Static

4. ADSL2 <--> ISP2 : ADSL. Static

I intend to enable load balancing for outgoing traffic base on 2 links. Can you propose me suitable solutions ?

[Gilles Dufour]

this is not loadbalancing as defined on this forum.

This is routing over multiple links.

Please post your question into Network Infrastructure -> routing/switching

A simple answer to your question is to use 2 default route. 1 pointing to each ISP over whatever link you have.

Doing a 'sho ip route static' you should see the 2 routes and an asterisk '*' after one of them.

This indicates the router is *loadbalancing* traffic over the 2 links and the next packet will be forward to the route marked with '*'.

Hope this helps.

Regards,

Gilles.

[paul.matthews]

You really should be pointing this at a routing forum!

What do you want to acheive on the outbound load sharing?

The simple option is to use two default routes. The 3725 will distribute the load across the two links.

You could have two slightly different routes

ip route 0.0.0.0 128.0.0.0 -> ISP1

ip route 128.0.0.0 128.0.0.0 -> ISP2.

And traffic wil go according to routes. This is not a great solution.

You could use policy based routing - http traffic goes to one ISP, anything else to the other as an example.

With PBR you need to think carfully about behaviour in the case of a link fail.

You also need to think about the return traffic - NAT hapennign somewhere outside your network could cause fun!