Reserved IP address: Linux vs Windows

April 7, 2008

I’m doing some refresh in my IP knowledge, and I was wonder for one thing: How different operating system behaves when you try to use a reserved IP address as the primary address of the system? So I do a simple test, put (at least try) a reserved address as primary address in a Linux box and in a Windows XP box.

The reserve address subject to this test are:
– the all 0’s ip address (0.0.0.0)

– loopback address (127.0.0.0/24)
– multicast range (224.0.0.0 – 239.255.255.255, or 224.0.0.0/4)
– reserve range (240.0.0.0-255.255.255.254 or 240.0.0.0/4)
– broadcast address (255.255.255.255)
Well, the results are what follow:
In Windows XP MCE I can’t use any reserved IP address, the TCP/IP configuration forbid to use any of this invalid for normal address as primary address.
In Linux (Fedora Core 7), I could put all sort of reserved address but 0.0.0.0/24. I use both CLI ip address add command and graphic interface system-config-network-gui.

The RFC 1700 (ASSIGNED NUMBERS), from 1994, use the concept of the IP address Class (created by original RFC 790, from 1981), marking class A, B and C as destinated for unicast address, D for multicast and E reserved for future use, and it reserve the block from 224-239, 240-255, 127/24, 0/24. This RFC make the use of class not so important, the classless, but still make the reservations.

This show Microsoft people more careful that the counterpart from Linux.

If I had time I’ll make some test in other platforms.

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