routing to multihomed server from LAN

mistral99 · 01-16-2012, 02:52 PM

Hi,

I have 2 servers:

ServerA (multihomed)
eth0: 192.168.100.76
eth1: 1.2.3.4 (public ip)

ServerB
eth0: 192.168.100.80

gw for 192.168.100.0/24 is 192.168.100.1 (firewall)

If I use traceroute to ServerA's public ip from ServerB, it goes there in 2 hops, the first one being the gw (firewall):

traceroute 1.2.3.4
1 192.168.100.1
2 1.2.3.4

Can I reach ServerA's public ip directly (in 1 hop)?

On serverB I tried:

ip route add 1.2.3.4/32 via 192.168.100.80 dev eth0

but that didn't help.

Thanks.

T3RM1NVT0R · 01-16-2012, 03:40 PM

Hi mistral99,

Welcome to LQ!!!

Nope, it is not possible to reach the public IP address from server B directly because server B is part of different network then server A's public interface. So it has to go via default gw that is firewall in your case.

MartinStrec · 01-16-2012, 04:21 PM

When you use routing packets ever go through all hops as you described.

For to "hide" your inner network you another technique of transporting.

You can use IP tunneling see http://www.linuxfoundation.org/colla...king/tunneling
or Virtual Private Lan Service (such as mikrotik routers) http://wiki.mikrotik.com/wiki/Manual:Interface/VPLS
you can download the VPLS for Linux.

mistral99 · 01-17-2012, 08:39 AM

Quote:

Originally Posted by T3RM1NVT0R

Hi mistral99,

Welcome to LQ!!!

Nope, it is not possible to reach the public IP address from server B directly because server B is part of different network then server A's public interface. So it has to go via default gw that is firewall in your case.

Thanks, that makes sense - since it's the same box I thought there might be a way. I will look into IP tunneling as MartinStrec suggested, but in the meantime, I changed the applications to reach Server A thru its lan interface. (ServerA is used as a RTP/SIP proxy and handling NAT is not always straightforward.)

TimothyEBaldwin · 01-31-2012, 08:27 AM

You want to do:

Code:

ip route add 1.2.3.4/32 via 192.168.100.76 dev eth0