So I have a server set up with 2 ppp interfaces.

ppp0 = fast capped at 5GB/m
ppp1 = slow uncapped

I have set up a second proxy server listening on port 8888 on the server. I am trying to route all of those requests through the slow interface and have everything else run through the fast interface.

My ideal set up is to get torrents to run through the slower one (similar to http://www.linuxquestions.org/questi...erface-792766/) but I'll try that once I've gotten this working (as far as i know torrents use a specific port range so it shouldn't be that tricky to adapt this)

As far as I know, it involves 3 steps.
Step 1 - Mark packets in firewall
Step 2 - Create a routing rule to send all marked packets to a specific lookup table
Step 3 - Set the default route for that lookup table to the gateway + dev for the interface.

I have marked the packets in the firewall as when I access the proxy I can see the requests in the firewall logs.

I don't need it on the OUTPUT table as this is only for pc's behind the NAT, not the server itself.

I have added the tables into /etc/iproute2/rt_tables:

Then the iproute2 magic:

tcpdump listening on ppp1 sees nothing.

I don't really know what else to do here? I've literally spent over 20 hours on this over the past few months! About to go crazy here!

ppp2 ?

Sorry, my bad. I'll edit my post - it was meant to say ppp1

Just my 2c worth....this may be way off the mark, but....

It looks like you want to do someting like what I do to feed my HTTP traffic through my Proxy, but I do the redirect a simpler way than writing direct to IPTables...would it not be simpler to use s a front-end (I use shorewall) and just tell shorewall to capture and redirect certain traffic to a different interface? I may be misinterpreting what you are doing, and respect is due if you manually hack IPTables, but I'm trying to see a simpler way of doing what you are doing.