I have a strange problem with a Linux router.
The setup is like this:
host1 === Linux router === host2 a.b.c.d --- a.b.c.e/g.h.i.j --- g.i.h.k
Every five minutes host1 tries to reach host2.
If host2 is down, the Linux router makes an ARP request for a.b.c.d on the left network with address g.h.i.j (i.e. from network on the right side). After receiving the MAC address from host1 the router sends an ICMP-unreachable packet with g.h.i.j as sender address.
If host2 is up, everything is fine. The router makes the ARP request with its address a.b.c.e.
On the router I have
$ uname -a Linux pfc 3.6.9-voyage #1 SMP Tue Dec 11 09:53:27 HKT 2012 i586 GNU/Linux
There is no proxy_arp involved.
The problem is: in my eyes the route should not use the IP address from the right hand network for the ARP request. Or am I missing something here?