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" 127
network traffic as follows:

Machine 1:   ifconfig eth0:1 127.1.2.3   [ running kernel 2.2.14 ]

Machine 2:   ifconfig eth0:1 127.1.2.4  [ running kernel 2.4.19 ]

Machine 2:  ping 127.1.2.3

Packets move between the hosts.    Also seems to work on Macintosh.

tc