routing traffic based on port

[eworlds]

I have been looking around but obviously havent typed the right combo of words into google yet.

We have a system with a primary link through which most of our traffic goes, however this is not controlled by us (and has some major limitations regarding blocked ports etc). We also have a DSL link which we would like to be able to send some traffic over.

We have managed using routing (on an IPCOP box) to send some stuff based on address range via the DSL but we would like to be able to send stuff out based on port. Is this possible? for example NTP for network time sync is currently blocked via our main provider so we would like all NTP requests to be routed via our DSL etc.

Cheers
Allan

[anomie]

I'm sure this is possible with any modern packet filtering firewall (e.g. iptables/netfilter), but to me it is much simpler to use something like rinetd.

It's easy to configure and will forward TCP traffic.

[eworlds]

that would forward connections made to our firewall to a to a specific port to another machine (which the firewall can already do) but what I am wanting to do is route any traffic on specific ports from inside our network our via a specific link.

[anomie]

I see what you're asking now.

Route internal client traffic based on external service port requested... no ideas.

[anomie]

A quick google for 'iptables route target' and I found this:

Netfilter Extensions HOWTO: New netfilter targets

See the ROUTE Patch section.

It's the first I've heard of it, but it sounds like it may meet your needs.

Good luck.