saias12 /ms/user/g/goliaa 1$ ip addr show
1: lo: <LOOPBACK,NOARP,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
inet 172.31.254.254/32 brd 127.255.255.255 scope global lo:0
2: eth0: <BROADCAST,MULTICAST,NOTRAILERS,UP> mtu 1500 qdisc pfifo_fast qlen 100
link/ether 00:50:8b:75:f7:58 brd ff:ff:ff:ff:ff:ff
inet 172.31.245.41/24 brd 172.31.245.255 scope global eth0
3: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 100
link/ether 00:50:8b:75:f7:57 brd ff:ff:ff:ff:ff:ff
inet 172.31.246.41/24 brd 172.31.246.255 scope global eth1
load balancing outgoing traffic out both subnets with two def routers of equal weight:
saias12 /ms/user/g/goliaa 2$ ip route show 172.31.246.0/24 dev eth1 scope link 172.31.245.0/24 dev eth0 proto kernel scope link src 172.31.245.41 127.0.0.0/8 dev lo scope link default nexthop via 172.31.246.1 dev eth1 weight 1 nexthop via 172.31.245.1 dev eth0 weight 1
iptables -t nat -A POSTROUTING -p tcp -m tcp --dport 9 -j SNAT --to 172.31.254.254
cause i want all outgoing traffic on port 9 to go out with that src ip. that works. but when the traffic comes back in, it gets changed to the ip of one of eth0 or eth1. why? FYI: this doesn't happen if i have just one default router:
start a tcp connection from this machine to 144.14.15.234 (just some other machine):
saias12 /ms/user/g/goliaa 2# tethereal -i eth0 -f "port 9" Capturing on eth0
0.000000 172.31.254.254 -> 144.14.15.234 TCP spidrweb > discard [SYN] Seq=3422061520 Ack=0 Win=5840 Len=0
0.002121 144.14.15.234 -> 172.31.245.41 TCP discard > spidrweb [SYN, ACK] Seq=3425048263 Ack=3422061521 Win=5792 Len=0
the first pkt is expected (src ip got changed by NAT). But the second pkt got changed to the IP of eth0. But 144.14.15.234 did not send the pkt to 172.31.245.41, it sent it to 172.31.254.254.
-- Cheers, Anthony
