[LARTC] Adv routing features

[LARTC] Adv routing features

[suresh]

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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