Routing with VPN and asymmetric communication
- by Louis
I'm stumbling on a problem that requires your advice.
Keywords : networking, route, openVPN
Problem : I have a local network with several physical servers and VMs. These machines have ip's in the range 10.10.x.x. I can access these machines from the Internet with the help of openVPN. These machines can :
access each other within the local 10.10.x.x subnet
access the Internet via the VPN
can themselves be accessed (via SSH) from the Internet via the VPN.
There is one machine however that behaves strangely and I don't know why. I can SSH into this machine from anywhere via SSH and I can also PING it from anywhere (including the Internet). However from this machine (i.e. when logged into it) I cannot access the Internet or ping machines outside the local network. In other words it will not go beyond the VPN. My question is why? Here are some technical details:
The machine's Network Config (running Debian 6.0.3):
allow-hotplug eth0
iface eth0 inet static
address 10.10.10.200
netmask 255.255.0.0
network 10.10.10.0
broadcast 10.10.10.255
gateway 10.10.10.200
The machine's Routing :
Destination Gateway Genmask Flags MSS Window irtt Iface
127.0.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 lo
10.10.0.0 10.10.10.250 255.255.0.0 UG 0 0 0 eth0
10.10.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
0.0.0.0 10.10.10.250 0.0.0.0 UG 0 0 0 eth0
0.0.0.0 10.10.10.200 0.0.0.0 UG 0 0 0 eth0
The VPN's Network Config (running Debian 6.0.3):
# This is the local network interface
auto eth1
allow-hotplug eth1
iface eth1 inet static
address 10.10.10.250
netmask 255.255.0.0
broadcast 10.10.10.255
gateway 10.10.10.250
The VPN's routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
10.10.0.0 0.0.0.0 255.255.255.0 U 0 0 0 tun0
private 0.0.0.0 255.255.255.0 U 0 0 0 eth0
10.10.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1
0.0.0.0 10.10.10.250 0.0.0.0 UG 0 0 0 eth1
0.0.0.0 private 0.0.0.0 UG 0 0 0 eth0
net.ipv4.ip_forward = 1 on both machines.
there are no iptables set anywhere.
Thanks in advance for any feedback.
