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SubjectRe: Problem: RFC1166 addressing

You are correct sir. I was just quite surprised to find that it works,
and that I can reassign the 127 network to any interface I like.


Gerhard Mack
<gmack@innerfi To:> cc:
Subject: Re: Problem: RFC1166 addressing
09/16/02 12:25

On Mon, 16 Sep 2002 wrote:

> Date: Mon, 16 Sep 2002 11:50:36 -0500
> From:
> To:
> Subject: Problem: RFC1166 addressing
> RFC 1166 states that:
> The class A network number 127 is assigned the "loopback"
> function, that is, a datagram sent by a higher level protocol
> to a network 127 address should loop back inside the host. No
> datagram "sent" to a network 127 address should ever appear on
> any network anywhere.
> Linux does not enforce this. I have uncovered some users using this
> function to attempt to circumvent the firewall. I am able to "create"
> network traffic as follows:
> Machine 1: ifconfig eth0:1 [ running kernel 2.2.14 ]
> Machine 2: ifconfig eth0:1 [ running kernel 2.4.19 ]
> Machine 2: ping
> Packets move between the hosts. Also seems to work on Macintosh.

I would call that a bug in the firewall rules. Depending on the hosts to
behave in such a way as to make life easier for the firewall makes for a
losing proposition.


Gerhard Mack

<>< As a computer I find your faith in technology amusing.

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