Dual-homed DHCP Gateway Selection

English Network/Internet
#1

Running openSUSE 10.3, dual-homed as follows:

eth0 - LAN
eth1 - WAN (ISP)

Both NICs are using DHCP. Via DHCP assignments, the default route assigned is from my LAN DHCP server. My ISP also assigns a gateway, but it doesn’t stick and I have to manually reconfigure routing after each boot. This machine is my internet firewall so I need the gateway to use my ISP’s setting.

Is there a way to get the gateway from my ISP to take precendence? I don’t want to configure it statically via the Default Gateway option as my ISP sometimes changes their setup which could make a static configuration invalid.

–bd

#2

You can add a script in /etc/init.d/after.local.
Here is example:
LAN Network: 192.168.1.x
LAN Gateway: 192.168.1.1

Below is script:

#!/bin/sh
ifdown eth0
ifdown eth1
ifup eth0
ifup eth1
route delete -inet 192.168.1.x network 255.255.255.0 gw 192.168.1.1

#3

Yeah, I thought of writing a script right after I posted. I wrote one that works a treat, but apparently after.local isn’t the right place for it as it doesn’t kick in after booting. Guess I’ll have to do some digging re: where it should go. In the meantime, here’s the script:

sfile=/var/lib/dhcpcd/dhcpcd-eth1.info
gw=grep GATEWAY $sfile
gw=echo $gw | awk -F "=" '{print $2}'
route del -net 0.0.0.0
route add -net 0.0.0.0 gw $gw

Oh, and the reason I didn’t think of a script earlier is because I have a SLES 9 machine with the same NIC config, and the gateway from its eth1 is the one that sticks. I just can’t figure out how I got that to work. :wink:

–bd

#4

/etc/init.d/after.local
This file is workable.
You can see /etc/init.d/rc to obtain more information.

#5

/etc/init.d/after.local works if I change runlevels, which is what the rc file indicates should happen. It does not seem to execute as part of the boot process however, which is where I need it.

–bd

#6

Did you add #!/bin/sh in your head of script?

#7

No, I had not included that. But I just added it as the first line of the script and the script still doesn’t execute during the boot process.

–bd

#8

The after.local script can’t execute during the boot process that is strangeness.
I have never seen that.
Do you define the same variable of script?

gw=grep GATEWAY $sfile
gw=`echo $gw | awk -F “=” ‘{print $2}’

#9

Well, this turns out to be a matter of patience. The script is running after all – I was testing for it too soon after bootup. If I logged in immediately after booting and then ran the route command, the eth0 gateway was listed, so I presumed the script wasn’t running. In reality, it had not run yet, and if I waited another 15 seconds or so, the script would run and the route would change.

So, thanks for your help and sorry I took us down the wrong path!

If I ever figure out how I got this working on SLES 9 without the script workaound, I’ll post back…

–bd

#10

OK, I finally figured out a more proper solution to this problem…

In the /etc/sysconfig/network/ifcfg-* files, enter the following as appropriate for the interface being configured:

DHCLIENT_SET_DEFAULT_ROUTE=“yes|no”

Setting this to “no” on my private interface and to “yes” on the public interface solved the issue for me.

–bd

#11

That’s a good news.
Your problem can be fixed by yourself.