Multiple ISP routing by port

[Max Laier]

On Tuesday 27 January 2009 06:18:09 jmaps-fbsdnet at fireburns.net wrote:
> I've read through what I could find in this list and also in the top 50
> results on google... I can't find anything that'll actually make this work.
>
> My DSL ISP is too far away to give me anything faster than 1.5mbps down. In
> despiration I signed up for comcast to use for bulk traffic.
>
> Thus, I want to route critical traffic (22, 25, 53, (maybe) 80, 443)
> through the DSL provider and the rest through cable.
>
> I really feel like this should be possible with PF with something like:
>
> nat on $dsl_if from ($int_if:network) to any port $dslports -> ($dsl_if)
> nat on $cbl_if from ($int_if:network) to any -> ($cbl_if)
>
> or
>
> pass in quick on $int_if route-to { ($dsl_if $dsl_gw) } proto { tcp udp }
> from ($int_if:network) to any port $dslports
>
> Neither (or both) seem to do it. All traffic ends up getting routed through
> whichever ISP i have set as the default route.

Take a look at: http://www.openbsd.org/faq/pf/pools.html#outgoing

You are probably missing the following part of the setup:
| To ensure that packets with a source address belonging to $ext_if1 are 
| always routed to $ext_gw1 (and similarly for $ext_if2 and $ext_gw2), the 
| following two lines should be included in the ruleset:
|
|    pass out on $ext_if1 route-to ($ext_if2 $ext_gw2) from $ext_if2 \
|       to any
|    pass out on $ext_if2 route-to ($ext_if1 $ext_gw1) from $ext_if1 \
|       to any 

This obviously has to be adapted for you specific setup - but in general this 
works as expected.

> Now, I hear i can go over to linux and just configure both default routes
> at the same time (trivial with iproute2). But I'd rather avoid that if at
> all possible.
>
> Is there some trick I'm missing? Does quagga (bgpd) allow for this kind of
> routing scheme?

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