[LARTC] Multiple Internetconn. & DNAT

[Peter Huetmannsberger <huetmann@site38.ping.at>]

Hello, 

I came across a problem today, which after trying a number of approaches I 
could not solve, and I am hoping someone out there knows how to deal with 
this.

Situation: 

2 different internet connections on eth2 and eth3 

Traffic coming in on eth2 goes out on eth2 and traffic coming in on eth3 
goes out on eth3 (because of rt_tables, and routes, which works fine) 
unless I do a DNAT to a different machine. 

i.e. 

default route is eth3 

traffic comes in eth2 --> DNAT --> eth1 
machine behind eth1 answers correctly, but the resulting packets choose 
the default route (eth3) to go out and not the way they came in. 

or in ipaddress description: 

default route is 81.223.13.xx1

eth3 = 81.223.13.xx2
eth2 = 91.112.38.xx8

Packets coming in via 91.112.38.xx8 for port 80 get DNATed to 
192.168.10.199:80 
on returining from 192.168.10.199 they choose the default route 
81.223.13.xx2 on their way out. 

Without the DNAT the setup works fine, with the DNAT they don't. 

I am grateful for any suggestions.

Thanks 

.peter



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