Multiple ISP's on one Server

[Nifty Hat Mitch]

On Fri, Oct 01, 2004 at 09:41:46PM -0400, Sam Varshavchik wrote:
> Thom Paine writes:
> 
> >I ran into a small problem last month in that I used over 70G of
> >bandwidth. My current ISP can't really handle that, as it costs him $4
> >per G of transfer.
> >
> >I really need the static IP that he provides, as well as the discount on
> >my internet....
....
> >I need my current static IP to connect to servers I support, but I would
> >rather have most of my incoming connections as well as most of my
> >internet traffic head out the cable one.

Commonly the static IP address is for incoming connections and packets.
You can use either of your ports for a reply unless the far host
is doing something 'interesting'.

> All Internet traffic to your static IP address will go over the
> connection to your first ISP.  End of story.

How is routing configured.

Are both IP services routed nets.

In some cases it is possible to setup routing metrics
so your favorite connection is used more than another.

The obvious one is the default route.
You should not have a default route if both
are to be active.

If your default route is the inexpensive route
then outgoing data should do the right thing.

If you watch your traffic you can apply  outgoing routes 
to specific nets so the other link is used.
i.e. Outgoing traffic is almost easy.

> If you set up your default route through the cablemodem interface,
> all your outgoing connection will, by default, get your cablemodem's
> IP address, and go out via the cablemodem.  So, if most of your
> bandwidth is from your outgoing connections, just adjusting your
> default route will probably solve your problem.

Routing with multiple ISPs can be interesting.   It is the first 
thing to try (see above) but the last thing I expect will work.

ISPs work hard to manage bandwidth.  If you publish a route from ISP-A
to ISP-B you may find that more traffic than you expect flows through
you and you will be using more bandwidth than you expect.

> Note that if you download stuff from the web, you're actually originating 
> the outgoing connection, so it'll go over the cable.

Routes and Return routes are interesting. see traceroute and ping -R
and the need for ICMP packets.  Many hosts ignore or discard
RECORD_ROUTE option.

Have you looked at all the bells and whistles in zebra and 
other router tools.


-- 
	T o m  M i t c h e l l 
	Me, I would "Rather" Not.