Disabling eth1 NIC?

SlowCoder · 02-21-2007, 01:07 PM

I have a firewall whose eth1 nic needs to be able to be disabled/enabled quickly by cli, effectively stopping and starting all traffic through that interface. The OS is Slackware. Can anyone help with this?

MS3FGX · 02-21-2007, 01:13 PM

To shut down the interface, you just need to run the command:

ifconfig eth1 down

To start it back up, do:

ifconfig eth1 up

SlowCoder · 02-21-2007, 01:19 PM

Does this look like the answer? http://www.yolinux.com/TUTORIALS/Lin...html#STARTSTOP

Are there any issues I should consider before running the commands, such as will the firewall remember the last setting after a reboot?

acid_kewpie · 02-21-2007, 04:04 PM

config changes like this will not persist a reboot. this is for live changes only. on a reboot, original config files are reread, so you would need to edit those.

SlowCoder · 02-21-2007, 04:34 PM

Ok, I tried it out. Using 'ifconfig eth1 down' it shut down the interface as expected. When I brought it back up with 'ifconfig eth1 up', none of the computers on the network could connect to the Internet. I had to reboot the firewall to reestablish the connection. How do I fix this without rebooting?

SlowCoder · 02-26-2007, 11:47 AM

... bump ...

Can anyone help with my last question? Viewing a printout of the route, it looks like that's where it's missing info. So I'm thinking I need to rebuild the route table?

nx5000 · 02-26-2007, 11:58 AM

The easiest is to use ifup and ifdown commands.
Basically it's supposed to do:
1)ifconfig eth1 up
2)route add default gw <defaultgw>
3)modify your DNS settings in /etc/resolv.conf

ifup eth1
ifdown eth1

SlowCoder · 02-26-2007, 12:01 PM

So I MUST re-add my gateway back into the route each time I bring it down and up again? Is this the easiest way to reestablish the connection?

nx5000 · 02-26-2007, 12:08 PM

Quote:

Originally Posted by SlowCoder

So I MUST re-add my gateway back into the route each time I bring it down and up again?

Yes, point 2. Also check that your /etc/resolv.conf contain your dns server adress (should be okay).

Quote:

Is this the easiest way to reestablish the connection?

"reestablish the connection"? Not sure I understand. You mean how to redo the configuration of the routes?
ifup

SlowCoder · 02-26-2007, 12:15 PM

Yeah, my DNS is fine.

In order to reestablish the connection, I use 'ifconfig eth1 up', which I think is the same as 'ifup eth1'?. I don't physically disconnect the cable. I was hoping for a single command solution that would bring me up and down quickly, as this is a firewall for my work.

In case it's not clear what I'm trying to do: What I want to do is simply stop traffic on the interface, then resume.

nx5000 · 02-26-2007, 12:34 PM

Quote:

Originally Posted by SlowCoder

I use 'ifconfig eth1 up', which I think is the same as 'ifup eth1'?.

It looks like you did'nt read my initial post

ifup does plenty of things (I only listed 3 of them), not only ifconfig.

SlowCoder · 02-26-2007, 12:39 PM

Quote:

Originally Posted by nx5000

It looks like you did'nt read my initial post

ifup does plenty of things (I only listed 3 of them), not only ifconfig.

Actually, I did read it. I just MISREAD it!

Now that I've REREAD it I see what you're talking about. I'll give it a go. Thank you very much for your help.