Workaround for mpd5 and 8.0 broken proxy arp?

[Li, Qing]

Hi Ruslan,

Yes, I can reproduce this issue. The patch is still necessary, however, 
it does not resolve the if_ng issue because if_ng is a virtual interface
that is not really associated with any physical nic. The physical NIC is
where all of the entries (including the proxied entries) are kept.

Let me put some thoughts into how to resolve this problem.

> 
> If you change the ifconfig command shown there so that the local end
> of a P2P interface is assigned the same IP address 10.25.1.244 as of
> vlan408, it will work as expected.
> 

Right, doing so allow the networking kernel to find the correct physical
NIC.

-- Qing