[LARTC] Setting up split access

[LARTC] Setting up split access

[Christoph Georgi]

Hi,

I have a question concerning the configuration of multiple uplinks as 
described in the lartc howto, chapter 4.2:

I have a scenario as described in the lartc in Chapter 4.2 (Routing for 
multiple uplinks/providers), i.e. one linux router with two uplinks:

* 2 Mbps low delay DSL connection on device eth0
* 256 kbps higher delay DSL connection on device ppp0

I'm routing packages according to the service:

* http, VoIP and ssh over eth0 (priority traffic)
* everything else over ppp0 (non-priority traffic)

I do also require some non-priority traffic to use the route over eth0.

So I set up netfilter rules to mark the traffic accordingly:

* no mark for default/non-priority traffic to be routed over ppp0
* -j MARK 1 for priority traffic to be routed over eth0
* -j MARK 2 for traffic always over eth0

Then I set up the following additional routing tables:

* 201 for priority traffic:
   'default via <gateway of isp1> dev eth0

* 202 for traffic static over eth0
   'default via <gateway of isp1> dev eth0

I left the default routing table (254) unchanged except for the default 
route:
   'default via <gateway of isp2> dev ppp0

As described in an earlier post in this list, the rp_filter has to be 
disabled and the traffic for eth0 has to be SNATed to the IP of the 
interface as the kernel uses the IP of the ppp0 interface as source IP 
of every package.

However, I do not require to set up any other fancy routing entries 
described in the lartc howto to make the whole thing to work. The 
question is, am I missing an important point here?

Furthermore, I don't get how the routing entries as described in the 
howto ensure that traffic is routed out over the same interface as it 
was originally comming in. I only see rules that match outgoing traffic, 
but none that matches incomming traffic. Maybe someone has a spare 
minute to enlighten me ;)

thanks in advance
christoph


-- 


Christoph Georgi
-----------------------------
email.  christoph.georgi@web.de
fon.	+64 (0)9 815 8259

registered linux user #380268
ubuntu 5.04 (ubuntu.com)
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