So lets start by defining what ip aliases are. I put these in the same category as virtual interfaces. In other words these are not physically connected interfaces but are stacked on top of the main interface, in most cases this is eth0.

First lets take a look at the actual perl script. In this case I called it ipaliases.pl and I chmoded it to +x. I also stored this script in /etc/global/ (my nice default for custom scripts on my boxes). The script is rather simple in the fact that it opens /etc/ipaliases for reading as the variable ipaliases. We then do a while loop on the file and use the system command to output the exact text line by line thats listed in that file.

##


#/bin/perl


#


# network       Perl script to quickly bring up IP aliase interfaces


#


##


 


open(ipaliases, "/etc/ipaliases");


 


while() {


 


system($_);


 


}

Next is our /etc/ipaliases file which looks like below:

ifconfig eth0:2 192.168.1.102 netmask 255.255.255.0 broadcast 192.168.1.255


ifconfig eth0:3 92.168.1.102 netmask 255.255.255.0 broadcast 192.168.1.255


ifconfig eth0:5 12.68.12.98 netmask 255.255.255.0 broadcast 192.168.1.255

As you can see this is what a hand upping of an interface looks like. And lastly I added this line to the /etc/rc.local on a independent line:

perl /etc/global/ipaliases.pl

So now on reboot those will be automatically added back in to the system.