Re: [LARTC] ppp0/ppp1 ssh

From: Ramin Alidousti <ramin@UU.NET>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] ppp0/ppp1 ssh
Date: Sat, 28 Apr 2001 19:45:47 +0000	[thread overview]
Message-ID: <marc-lartc-98848724822638@msgid-missing> (raw)
In-Reply-To: <marc-lartc-98848046611913@msgid-missing>

On Sat, Apr 28, 2001 at 01:53:00PM -0400, Jettero Heller wrote:

> This seems so simple I can't believe it doesn't work yet.
> I have two modems connected to two ISPs.  I route everything
> through the "fast" one with:
>     ip route default via xxx.xxx.xxx.xxx dev ppp0
> 
> Then to the machine I regularly tf and ssh, I add this:
>     ip route tf.tf.tf.tf     via xxx.xxx.xxx.xxx dev ppp1
>     ip route ssh.ssh.ssh.ssh via xxx.xxx.xxx.xxx dev ppp1
>     
> The reason I joined this list is that I'd rather do
> something like this, but I can't get it to work right.
> 
>     ip route add default via xxx.xxx.xxx.xxx dev ppp1 tos 0x10
> 
>     for i in 22 23 8000; do 
>         iptables -t mangle -A PREROUTING -p tcp 
>                  --dport $i -j TOS --set-tos 0x10; done
> 
> I would have figured everything for port 22, 23 and 8000
> would go out ppp1 and come back ppp1, but I was rather
> suprised to find that _all_ my traffic goes out ppp0, but
> the stuff I tagged 0x10 comes back in ppp1?!?

Good question. First of all I'm not sure that TOS would influence the
routing decision, either on your Linux box or on the routers out there.

The reason that the packets come back on ppp1 is that the source of the
IP is set to ppp1 (which is weird, when you're saying that the packets
go out on ppp0 to ISP I, are you sure about this?). Then the returning
packets which are destined for ppp1 (which belongs to ISP II) will get
routed on the Internet to ISP II and will be delivered to PPP1.

Again, if you want to route different services through different ISP's
it is called policy routing. Take a look at the documentation on:

http://kewl.phear.org/policy/

Or Arthur's answers to the very same questions on this mailing list.

http://mailman.ds9a.nl/pipermail/lartc/2000q4/000091.html
http://mailman.ds9a.nl/pipermail/lartc/2000q4/000092.html
http://mailman.ds9a.nl/pipermail/lartc/2000q4/000153.html
http://mailman.ds9a.nl/pipermail/lartc/2000q4/000156.html

Ramin

> 
> What am I missing?
> 
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