MDLog:/sysadmin

The Journal Of A Linux Sysadmin

Linux Tips: How to Quickly Bind a Range of IPs on RedHat Based Systems

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In this short post I will show you how you can quickly add a range of IPs on any RedHat based system (Rhel, Centos, Fedora, etc). When you have to add many IPs to a system this can be quite handy and save a lot of time. Normally when you add a new IP to a network interface in a RedHat based system you create a file ifcfg-eth0:x in /etc/sysconfig/network-scripts/. For example:

/etc/sysconfig/network-scripts/ifcfg-eth0:0
DEVICE=eth0:0
ONBOOT=yes
BOOTPROTO=static
IPADDR=192.168.0.100
NETMASK=255.255.255.0
NETWORK=192.168.0.0
BROADCAST=192.168.0.255
TYPE=Ethernet

Similar to the above example you can create several aliases. But what if you have to add a lot of IPs that are in a range like this? Let’s say that I want to add 100 IPs this way… this is possible, but not very effective, right? RedHat based systems offer a method to bind a range of IPs in a quick way allowing us to eliminate the need to create a lot of files and saving us time doing this. Create a file /etc/sysconfig/network-scripts/ifcfg-eth0-range0 if this doesn’t exist, or just add to it if you already have it, the following lines:

/etc/sysconfig/network-scripts/ifcfg-eth0-range0
IPADDR_START=192.168.0.100
IPADDR_END=192.168.0.200
CLONENUM_START=0

where: IPADDR_START is the first IP and IPADDR_END is the last IP in the range. CLONENUM_START is the number that will be assigned to the first IP alias interface (eth0:0 in this example).

If you need to add more ranges of IPs then just use a different file for ex. ifcfg-eth0-range1, for each one of the ranges. You need to be careful and use the proper CLONENUM_START to not overwrite other aliases. Once you have configured the range/s of IPs you just need to restart the network service in order to activate it:

service network restart

Note: don’t use this method on a CPanel based system. Even though this will work fine, it is better to use CPanel/WHM in this case so CPanel can manage all the IPs properly. Here is a short post on how you can do the same thing ‘CPanel way’.

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