[ILUG-Cochin.org] Routing not possible in 'tun'

[Hrishikesh Murali]

Hi,

I have a computer with two NIC cards "eth0" and "eth1".

It is connected to a VPN server via eth0. The client "tun0" ip address is
"10.100.100.2" and the VPN server "tun0" ip address is "10.100.100.1".

I have eth1 connected to a different subnet "10.1.2.0/24" and ip address of
eth1 is "10.1.2.1". I want to ping from "10.100.100.1" to "10.1.2.1". I have
enabled forwarding from eth0 to eth1 and have done NATing for packets going
out of eth0. But I am not able to ping from "10.100.100.1" to "10.1.2.1".
All is see in wireshark is a ARP broadcast saying "who has 10.1.2.1? tell
10.100.100.1". There is no reply to that broadcast.

The strange thing is that I am able to ping from "10.100.100.1" to
"10.1.2.1" without forwarding of any sort if I use a "tap" adapter in the
VPN.

1) Why is it so?
2) Any suggestions as to how I can do the same thing using the "tun"
adapter?

-- 
Thanks and Regards,
Hrishikesh Murali
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