help with one-armed routing

Eric Louie 21 years ago

Hi folks I have a configuration that I need help with

Here is the scenario - router with 2 fast ethernet interfaces, and one serial interface default route is out the serial interface the 1st fast ethernet interface is enabled the 2nd fast ethernet interface is shutdown

I want to use the 2nd fast ethernet interface as a one-armed router, independent of the rest of the router. It cannot allow any traffic to pass through, it can only bounce traffic.

Here are the conditions for that 2nd fast ethernet interface: if the source IP is 192.168.151.0 /24 then route it - if it is not that, then drop it.

if the destination IP is 192.158.55.0.0 / 24 then send it to 192.168.151.254

otherwise, send the traffic to 192.69.151.1

Anyone game to help me with this configuration?

thanks Eric

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Barry Margolin 21 years ago

You should be able to do this with policy routing.

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Eric Louie 21 years ago

yes, that's part of it, Barry, thank you. I completed that part of the config already

The other part is isolating this interface from the rest of the router. I guess I need help with those access lists and how/where to apply them.

thanks

-e-

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Barry Margolin 21 years ago

The easiest way is an "out" ACL on the 2nd FE that only allows traffic if the source address is in one of the subnets connected to that interface.

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Eric Louie 21 years ago

thanks again Barry. what I actually did was filter on the other two interfaces, to prevent them from accepting packets from the 2nd FE and from forwarding packets to the 2nd FE.

-e-

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Barry Margolin 21 years ago

In my last post I was originally going to mention that you can do it either way. But I decided not to mention this possibility, since it seems clearly simpler to have a filter on one interface than on two.

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