Hello Bertl,
Let me explain with exact flow of packets in my LAN to INTERNET
I N T E R N E T
/ \
------------- -------------
| a.b.c.e | | w.x.y.u |
| router1 | | router2 |
------------- -------------
\ /
\ /
\ /
-----------
| Switch |
-----------
|
|
|
eth1 eth1 a.b.c.d gw a.b.c.e
-------------- eth1:0 w.x.y.z gw w.x.y.u
| |
| linux |
| |
-------------- eth0 172.16.1.1
eth0 eth0:0 192.168.1.1
|
|
I want to forward all packet from 172.16.1.0/24 Network to router 1
and from 192.168.1.0/24 Network to router2.
In the linux box i am doing advance routing and iptables.
Here i am using iptables just for masquerading
the rules are
#/sbin/iptables -t nat -A POSTROUTING -o eth0 -p icmp --icmp-type ping -s
0/0 -d 0/0 -j MASQUERADE
#/sbin/iptables -t nat -A POSTROUTING -o eth0 -p tcp -s 0/0 -d 0/0 -j
MASQUERADE
Linux box's default gw is w.x.y.u and i added only following command
#echo 200 isp1 >> /etc/iproute2/rt_tables
#ip rule add from 172.16.1.0/24 table isp1
#ip rule ls
0: from all lookup local
32765: from 172.16.1.0/24 lookup isp1
32766: from all lookup main
32767: from all lookup default
#ip route add default via a.b.c.e dev eth1 table isp1
#ip route flush cache
It is not forwarding if packet from 172.16.1.0/24 but works fine if packets
from 192.168.1.0/24.
If i delete default gw and ip rule and add a.d.c.e as default gw than
packets from both networks forwarded to router1.
#ip addr
1: lo: <LOOPBACK,UP> mtu 16436 qdisc noqueue
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 brd 127.255.255.255 scope host lo
2: eth0: <BROADCAST,MULTICAST,PROMISC,UP> mtu 1500 qdisc pfifo_fast qlen 100
link/ether 00:06:5b:38:99:a8 brd ff:ff:ff:ff:ff:ff
inet 172.16.1.1/24 brd 172.16.1.255 scope global eth0
inet 192.168.1.1/24 brd 190.190.1.255 scope global eth0:0
3: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 100
link/ether 00:06:5b:38:99:a9 brd ff:ff:ff:ff:ff:ff
inet a.b.c.d/28 brd *.*.*.* scope global eth1
inet w.x.y.z/28 brd *.*.*.* scope global eth1:0
# ip route
*.*.*.*/28 dev eth1 proto kernel scope link src a.b.c.d
*.*.*.*/28 dev eth1 proto kernel scope link src w.x.y.z
172.16.1.0/24 dev eth0 proto kernel scope link src 172.16.1.1
192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.1
127.0.0.0/8 dev lo scope link
default via w.x.y.u dev eth0
Thanks
Suresh
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