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I would like to configure an IP address from class E, for example 241.0.0.2.

Currently Linux (Linux-2.6.21.7-hrt1) returns the following answer:

ifconfig: SIOCSIFADDR: Invalid argument

Is there a way to do this?

(The reason for using class E is that I would like to avoid IP address conflicts with customer IP networks.)

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migrated from stackoverflow.com Aug 28 '11 at 12:45

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Why do you want to do this? Can't you just use an A/B/C? –  DaveRandom Aug 28 '11 at 12:49
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The "Class E" address is a "range reseved for future use" - so nothing uses it, you'd not be able to communicate. –  rozcietrzewiacz Aug 28 '11 at 12:59
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Similar discussion: IPv4 Exhaustion: What About Class E Addresses? –  Steve-o Aug 28 '11 at 14:10
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4 Answers

The E class is not to be used. That is why the kernel does not permit setting such address. If you want a local IP, use one of the IP ranges designed for that purpose. Those are

10.0.0.0 – 10.255.255.255      (class A)
172.16.0.0 – 172.31.255.255    (from B class)
192.168.0.0 – 192.168.255.255  (from C class)

(See wikipedia for details.)

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+1 Concur. That's what those address spaces are bloody well for. –  Shadur Aug 28 '11 at 17:06
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I'll like to have internal IP communication between elements that will NOT conflict with customer IP networks

Sounds like a perfect time to implement IPv6.

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From an expired IETF draft "Redesignation of 240/4 from "Future Use" to "Private Use""

Apple OSX has been confirmed to support the use of 240.0.0.0/4 as unicast address space. Changes have been incorporated into recent versions of Sun Solaris and have been submitted for inclusion in the Linux kernel tree. No plans have been announced for modifications to any version of Microsoft Windows, in part because of uncertainty over how to perform 6-to-4 tunneling in the absence of a definitive statement on whether 240.0.0.0/4 is "public" or "private" space.

So the majority of operating systems will not support this address range even if you can force a device to use it.

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Use ip not ifconfig. Ifconfig is in the process of being deprecated by many linux distributions anyway.

ip addr add 241.0.0.2/24 dev eth0

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