VLANS + intervlan forwarding + SNAT

[Damien Mason <kinetic@suse.net.au>]

Hi All,

    Sorry I think my last post needs some clarification, so here it is, 
any help would be appreciated :)

I have the following setup:

Client Vlans (coming in on a single interface, trunked (802.1q).
   Client 1
       eth1.2    ip:    192.168.0.0/24
       eth1.3    ip:    192.168.10.0/24
       eth1.4    ip:    192.168.20.0/24
   Client 2
       eth1.5    ip:    192.168.0.0/25
       eth1.6    ip:    192.168.0.128/25

External Interface (to the internet) (examples only).
eth0:1       ip:    203.1.1.2
eth0:2       ip:    203.1.1.3
eth0:3       ip:    203.1.1.4
eth0:4       ip:    203.1.1.5

DMZ Intefaces, will not have overlapping network addresses.
eth2.1       ip:    10.0.0.0/24
eth2.2       ip:    10.0.1.0/24

I want to be able to enable clients on the eth1.x vlan interfaces to be 
able to:
   a) access the internet, that's easy, i've just setup masquerading.

   b) every 'client' has at least 1 external ip address, I want to be 
able to forward traffic to a vlan'ed server, that is, say traffic coming 
into 203.1.1.2 on port 80, is redirected to 192.168.0.10:80 on interface 
eth1.2, I cannot do this in iptables prerouting because you can not 
specify an outgoing interface in prerouting, if I could I would use 
something like:

iptables -A PREROUTING -t nat -p tcp -d 203.221.181.27 --dport 80 -j 
DNAT --to  192.168.50.10:80 -i eth1.2

But, of course, that's impossible.

So, if i use an snat setup, I've come up with something like:
iptables -t nat -A POSTROUTING -s 0/0 -d 203.1.1.2 -p tcp --dport 80 -j 
SNAT --to 192.168.0.10:80 -o eth1.2

Anything with a destination of  203.1.1.2, tcp, with a destination of 
port 80, nat it to 192.168.0.10, port 80, output on interface eth1.2


   c) inter-vlan routing/forwarding, eg. have hosts on (eth1.5 - 
192.168.0.0/25) access hosts (eth1.6 - 192.168.0.128/25)

Thanks in advance,

Damien Mason
SuSE Linux Asia-Pacific

Email: damien at suse.net.au 
<mailto:damien@suse.net.au?subject=Reply%20Email>
Web: http://www.suse.net.au./