How to add IP aliases

Date published: May 22nd, 2008
Posted in VPS | No Comments »

If you have been assigned extra IP addresses for a Xen VPS, here is how to configure them in your FreeBSD server.

open up /etc/rc.conf in your favorite editor

You should see a line that looks like this:

 ifconfig_re0=”inet 208.86.12.141  netmask 255.255.255.224″

Leave this line alone.  You can add your IP aliases in this fashion:

ifconfig_re0_alias0=”inet 208.86.13.50 netmask 255.255.255.255″
ifconfig_re0_alias1=”inet 208.86.13.51 netmask 255.255.255.255″

and so on.

Note that the netmask of alias IP addresses is always 255.255.255.255 (/32).  This keeps the network setup simple overall since only the first IP address has to have a broadcast and ARP entries.

Once the entries are in, reboot so you can make sure that they come up on boot properly.  You should now be able to ping your alias IPs from an outside host, assuming that you don’t have a firewall setup blocking ping traffic.

If you need additional IP addresses, you can request them by opening up a support ticket.  As always, we are available to assist you with this setup.  But you will probably find that it is easier than expected.   Please let us know if you have any questions.