Add a temporary static IP address

At home, with wired ethernet, my (Ubuntu) notebook has a few static IP addresses that I use for developing websites. Out of the house, I use wicd, so I have a dynamic IP address, and those static IPs don't exist. wicd configuration is too complex for me to understand, so I just accept this, but it caught me short the other day when I needed to have both an internet connection and to be able to work on a website running on my notebook.

I failed then, but I'm ready for next time. To temporarily add a static IP address you simply do (as root):

ifconfig eth0:3 10.10.10.10 netmask 255.255.0.0

I'm choosing "eth0:3" for the interface; it can be any unused number after the colon, and you never need to care what this is. netmask can really be anything for our purposes. The 10.10.10.10 is the IP address I've given it. Test with this:

ping 10.10.10.10

To set up a quick virtual host create a file under /etc/apache2/conf.d called 10.10.10.10.conf (any filename is fine) with these contents:

<virtualhost 10.10.10.10:80="">
    DocumentRoot "/var/www/somewhere"
    ServerName 10.10.10.10
</virtualhost> 

Tidyup

To remove just the interface that you added above, use this command:

ip addr del 10.10.10.10/32 dev eth0:3

Or, to restore the network to boot defaults (useful if you have done lots of changes) you can do:

ifdown -a
ifup -a

Either way to then remove the apache config: delete the 10.10.10.10.conf file you created and restart apache.