ARP is sourced from loopback address

William Herrin bill at
Tue Jan 31 00:09:36 UTC 2012

On Mon, Jan 30, 2012 at 6:24 PM, Joe Maimon <jmaimon at> wrote:
> Golden.
> Thank you, William.

Hi Joe,

You're welcome. The flip side of Linux's arp funkiness is that you can
get it to do some nifty stuff. For example, a /32 ethernet looks more
or less like this:

ifconfig lo:1 netmask
ifconfig eth1 netmask
ip route add dev eth1 src
arptables --out-interface eth1 -j mangle -s --mangle-ip-s

The implicit proxy arp takes care of the rest with the machine hanging
off the interface thinking that it's part of a /24.

This sort of thing is how I'm using all 17 of the IP addresses in my
Cox /28. :-)

Bill Herrin

William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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