Intranet & VPN Addressing Scheme

[maani]

I've seen on places organisations using 10.0.0.0 Address class for VPNs & Intranet, Can anyone guide me why use this particular class??

[Giuseppe Larosa]

Hello Maani,

network 10.0.0.0/8 is an IPv4 Private address per RFC 1918.

Usable Private addresses are the following:

10.0.0.0/8   taken from Class A major network

172.16.0.0.0 - 172.31.0.0.0 = 172.160.0.0/12 taken from Class B major networks

And

192.168.0.0/16  taken from Class C major networks 192.168.x.0/24 with x= 0-255

These addresses are to be used with NAT = Network Address Translation.

They allow for public IPv4 address space great savings because with PAT = Port Based NAT multiple private IP addresses can be translated to a single public IP address by using different TCP or UDP port.

Without private IP addresses that are not unique and that can be reused in multiple different companies, and without NAT IPv4 address space would have been totally consumed many years ago.

The long term solution for scalability is IPv6 that uses 128 bit wide addresses.

Mobile operators and Internet of things may be the trigger for extensive introduction of IPv6.

To be noted the use of private addresses allowed many companies to release their public IP address blocks.

In the past companies like IBM or Ford had their own Class A public IPv4 address like 20/8.

However, the IPv4 public address space has been finished few years ago.

Hope to help

Giuseppe

[maani]

You're right. As far as i remember, like 5 years ago when we setup a head office for a German company, their engineer in Berlin rejected our C Class typical IP Scheme 192.168.1.0 /24 by saying, we need 10.0.0.0 for our intranet to be connected with Berlin & GCC offices. Suddenly, after so long, I wanted to dig it up how & why its required for VPN & MPLS Intranet networks.

[Joseph W. Doherty]

It provides lots of "elbow room" for internal only (i.e. not on the Internet) IP usage, since the 10.0.0.0 is a class A or /8 address block. (NB: I've seen large organizations re-IP all their internal IP to the 10.0.0.0 address block, not just VPNs and Intranet. While doing so, often a nice addressing scheme [summary IPs for site or large blocks of hosts] can be implemented.)