I know I can rename my network interfaces (eg 'eth0' to 'lan', 'eth1' to 'net' etc) but does anyone know a way I can alias (symlink if you like) 'lan' -> 'eth0'

I want to be able to use more legible interface names in things like iptables rules (such as "-i lan" instead of "-i eth0") but I don't want to break any config that is expecting eth0 to exist....

Depending on your OS should be able to set this in udev.

in /etc/udev/rules.d grep for a file that has the eth definitions in it.

You should see a line like:Edit that file and change eth0 to whatever you want to call it.

Do not forget to update your network configuration files for the new name. RedHat like distros in /etc/sysconfig/network-scripts

Other methods of renaming interfaces include ifrename along with /etc/iftab or using the ip command.

Technically this shouldn't break anything, but who knows what apps are out there expecting interfaces to be called eth[0-9].

Let us know how it works out.

Traditionalists will use variable names that are meaningful and assign the actual eth0 or whatever values to them:

iptables=/sbin/iptables
internal_interface=eth0
internal_subnet=10.0.1.0/24


$iptables -A INPUT -i $internal_interface -s $internal_subnet ......

That way you get to keep the default names, you don't have to remember what jiggery pokery you went through to rename things, and nothing breaks.

Sorry, should have mentioned I'm specifically using CentOS 5.4 in this instance.

I don't want to change the current name, just create an alias/"symlink" from 'lan' to 'eth0'...

Yes, I could do that, but that means reinventing the iptables init script and discarding the stock one which I'd like to retain for simplicities sake (eg, when other sysadmins are on the box and don't know that it's actually "firewall" instead of "iptables" when calling service or chkconfig)... And I generally hate reinventing the wheel, especially for something as "small" as this

I use a script to generate the iptables rules (with the variables in it) then use iptables-save > /etc/sysconfig/iptables to save those rules in case of a reboot. Result is I get a readable script (with comments) that I can understand, but I don't have to change any inbuilt functionality.

That's not a half bad idea actually if I can't figure out how to do this.

Have a script generate a save file, then load that using iptables-restore. Has the benefit of being atomic so if there's a syntax error in the rules, it won't bork the current rules