Proxy arp

[john huttley]

This is not netfilter, but on the subject of arp..

I've been trying to set up a vpn with pptp

(test7)
I can dial in and get a connection, I can talk to the box but not off.to the
local sub net.
ahha!  ppp0 not on the local subnet and arp not being proxied.
Classic case. (ip_forwarding is on)


So switch on auto-proxy for eth0. No difference. For all interfaces. no
difference.
manually add arp entry. Find bug in kernel. nice man sends patch to arp.c.
Fix kernel, set up manual arp. still doesn't work.

Do slow burn. Try on another system where i can login to other machine on
sub net.
(2.2.16)

Repeat, no difference. On the other machine i'm running  'tcpdump -n -i eth0
arp'

proxying off, I would expect to see unanswered arp requests on the local sub
set.
dead silence on or off.

Stick the local and the remote ip address ranges to unused addresses on the
local subnet.
This should bypass any arp problems. Still doesn't work. And  forward is
definately on
because the box has an eth1 and talks to the outside with masquerading.

The catch is that I set up a similar system for a client using 2.3.99-pre7
which works
well.

I was wondering if setting up a LOG target would help in finding out what is
going on.
Trying to find out what happens to a packet inside the kernel seems very
difficult.

Yours in confusion.

John