[MLB-WIRELESS] Combining 2 internet conenctions.

[Tim Hogard]

The way this is supposed to work is...
You set up a server running a real os (freebsd,linux, solaris, osx)
and have it connect to both.  This is easier if you get three
ethernet cards but there are insane ways to do it with one.

You run dhcp clients on two and one will need bpalogin or a
router that can do the telstra stupidity.  I have no idea how
optus does its thing (pppoe? like adsl?)

Once things are connected, you want two default routes with the same
priority (but not the highest priority).

You then had a routes to the free sites.  You can add two routes,
one low priority and one very high priority.  If its a BP free site,
you list it with th eBP interface as highest priority and list it with 
Optus with lowest priority.  That way when BP goes down, you won't
notice.

If there is a site that you don't want to route to if BP goes down,
set up a high priority link to the BP interface and a lower (but higher
than any other routes) to the null interface (or 127.0.0.1 if you don't
have one).  This is handy for leaching links over wireless for example.

You need to run something that looks at your network stats (netstat is
your friend here), and when one of the links gets close it its limit, you
increase its priority a bit.

Also you can use names in route statements but it tends to be
host based.  Its handy for sites that are free but move around.
Just be aware that if a host has two address, only the 1st will
get listed.

You can also do interesting games with alais enterfaces (eth0:1 in linux),
for example, assume eth0 is set to BP and you create eth0:1 :2 and :3.
You can set up low priority routes for :3 when your capped to 64k and
:2 when your close to your limit and :1 at the start of the month.  Then
all you have to do is 'ifconfig eth0:1 down' when your at 9 gig, 
and down :2 when your at 10 and you never have to change a route.

You can do interesting tricks with ipfw under bsd with rule numbers
and inserting goto statements to bypass rules so you auto shape some
stuff before its a real problem.

If your into 24x7 leaching and always hit both caps, find a dialup and
add that into the route pool too.  You can have scripts that look at some
connections and start routing them other ways.

One thing to keep in mind is that routing only effects how packets leave
your system, not how they get back and thats what your paying for.  Nating
on the outbound interface is the easy way to fix that but it will mess
with active connections.

Of course if the APNIC got its act together and started assigning joint
IP address space, then we could do proper dual homing but I don't
see that ever happening.

-tim
http://web.abnormal.com

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