Load sharaing between DSL and T1 link on router

[egain.com]

hi

i have 2 x T1 terminating on border router cisco 3640 route. (configured using multilink interface). Our IP block is routed on this bundled T1 circuits by At&T.

I want more internet bandwidth.

1.  Can i connect my DSL (on ethernet interface and using static DSL IP) on the same router and confgure two static routes to internet - one to multilink interface and other to ethernet interface (connected to DSL) ?

2. I have many servers using static NAT to external IPs which are routed on T1 circuits. Will it get into issues when communicating to outside? [for example my exchange server, websites etc?

thanks

regards

rakesh

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[cadet alain]

Hi,

1) yes of course you can just configure 2 static default route with same AD one pointing to ethernet next-hop and the other to MLPP interface

as CEF is on by default then load-balancing will be per src-dst ip

2) you'll have to do something like this for static PAT

ip nat inside source static tcp x.x.x.x 80 y.y.y.y extendable

ip nat inside source static tcp x.x.x.x 80 z.z.z.z extendable

where y is for MLPP ip address and z for DSL ip address

if you're doing NAT overload then something like this

access-list 10 permit 10.0.0.0 0.0.0.255

route-map NAT1

match ip address 10

match interface

route-map NAT2

match ip address 10

match interface

ip nat inside source route-map NAT1 pool mypool1 overload

ip nat inside source route-map NAT2 pool mypool2 overload

where mypool1 is for MLPP and mypool2 is for DSL

Regards.

Alain.

[egain.com]

Thanks Alain.

I forgot to add one thing. - I already have ASA firewall connected to border router which is doing the NATing on ip block i have on T1 links. So every inside hosts after coming out of firewall has external IP address.

in this case, how ethernet interface (connected to DSL) can handle the internet requests? Can it do PAT again on ethernet interface ?

thanks

regards

rakesh

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[cadet alain]

Hi,

Can you post a diagram. Will your DSL go through the ASA also?

Regards.

Alain.

[egain.com]

let me try drawing it here -

                                                                          (NAT all internal)

--users 10.0.0.0---->core switch (4507) ----->  ASA 5520 ----- ----(Border router) == 2 serial interfaces - 2 x T1 externa IP block)

                                                                                                                                     ) === (proposed) 1 ethernet connecting to DSL

- users are connected to core switch (having 10.0.0.0 range IPs) - core switch will forward internet traffic to ASA - ASA is doing all NAT - ASA sends internet traffic to Border router - Border router (at present) has two serial interfaces connected to T1 links.

Thought is to connect ethernet interface of border route  to one of the swith port on DSL router/modem along with static address. (of DSL)

thanks again.

regards

Rakesh

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[cadet alain]

Hi,

then don't worry about NAT  as it done on the ASA and the ASA has only one link to border router.

So just connect your ethernet interface and configure a second default static route pointing to your DSL next-hop and it should be good.

Alain.

[egain.com]

Ok. thanks Alain. I guess the return traffic will route via T1 links (due to the NATed extenal address is from IP block that is routed on T1 links.

I will try this and let you know how it goes.

thanks.

regards

rakesh

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