How do load balancing in R3735 with 2 ADSL line ?

[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 ?

[david.bradley]

Assuming you have a matching setup at the remote end, you should be able to set up GRE tunnels between you 3725 and the remote router, then use RIP or preferably EIGRP to load balance between the 2 links.

[hungnt]

hi david !

I think you not completely understand my situation. So I will decrible again.

The routing protocol between Customer (like me) and ISP is static (they (ISPs) does not accept any dynamic routing thought xDSL connection).

The ADSL modems don't support dynamic routing, so the routing protocol between ADSL modem and Cisco 3725 is static routing only.

hope to receive your reply again.

thanks,

[david.bradley]

Hi,

I thought this was between 2 of your sites :)

Put two static routes in your router config to your ISP.. i.e.

ip route 0.0.0.0 0.0.0.0 fa1

ip route 0.0.0.0 0.0.0.0 fa2

If you look at you IP routes you should see both entries for the default route.

If you disable fast switching (no ip route-cache) you will have load balancing on a per-packet basis, rather than a per-destination. If you disable the fast switching the load on the router CPU will be higher.

Dave

[dnewell24]

Dave,

I initially thought the same thing. But if one of his DSL lines goes done wouldn't that black hole half his packets?

I guess as the administrator it his choice to determine whether or not he is willing to take the risk.

[hungnt]

hi Dnewell !

I completely agree with you in this point.

I'm trying to find a best solution for this case, but I can't.

When one DSL link go down, the Cisco Router (not the ADSL modem) can't detect so a haft of packets will fall into the black hole.

[spremkumar]

hi

I m also falling into the same line but i m trying to use a bri with DSL instead of 2 DSL lines,,

have u figured out the deployment of SAA based polic routing in this scenario ??

since i havent decided/sticked to tht yet i couldnt confirm about SAA..

regds

[cisand2002]

if you have static route as above and one of you fe go down, you will loose this route. So you will have only one remaining default route.

So load balancing from you routers to the isp's is ok. The problem is that you will not have load balancing from isp's to your routers.