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My home network has an OpenVPN server installed and working. I can connect into that network from Windows machines using the OpenVPN client software and everything works fine.

I have an Ubuntu laptop with the OpenVPN client installed. I can connect to the OpenVPN server using the client and the client.ovpn provided by my server; however, I cannot ping or access machines on the VPN once connected. Running a ping to a network machine results in this:

$ ping 192.168.2.3
PING 192.168.2.3 (192.168.2.3) 56(84) bytes of data.
From 192.168.2.136 icmp_seq=1 Destination Host Unreachable
From 192.168.2.136 icmp_seq=2 Destination Host Unreachable
From 192.168.2.136 icmp_seq=3 Destination Host Unreachable

The same thing works fine from Windows, so there must be an issue with how the routes are getting configured on the Ubuntu client, but I can't figure out what it is. I flushed my firewall rules on the client just in case.

Here's the output from route -n before and after the VPN connection:

107.15.x.x is the VPN network's public IP.
172.27.x.x represents the VPN's virtual network.

WITHOUT VPN

$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.2.1     0.0.0.0         UG    0      0        0 wlan0
192.168.2.0     0.0.0.0         255.255.255.0   U     9      0        0 wlan0
192.168.121.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr1
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0

WITH VPN

$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.2.1     0.0.0.0         UG    0      0        0 wlan0
107.15.x.x      192.168.2.1     255.255.255.255 UGH   0      0        0 wlan0
127.0.1.1       172.27.232.1    255.255.255.255 UGH   101    0        0 tun0
172.27.224.0    172.27.232.1    255.255.240.0   UG    101    0        0 tun0
172.27.232.0    0.0.0.0         255.255.252.0   U     0      0        0 tun0
192.168.2.0     0.0.0.0         255.255.255.0   U     9      0        0 wlan0
192.168.2.0     172.27.232.1    255.255.255.0   UG    101    0        0 tun0
192.168.121.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr1
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0

Any idea what I need to do to solve this?

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  • I don't understand what side you cannot ping when you say "I cannot ping or access machines on the VPN once connected". E.G. suppose you have a network printer attached to the same "local" LAN you're connected to before you VPN. Then you VPN into the "remote" LAN which contains only one server. Are you not able to ping the server or are you not able to ping the printer? – Fabby Nov 30 '14 at 1:21
  • I am unable to ping the "remote" LAN systems from the workstation acting as the VPN client. – Matt Hamann Nov 30 '14 at 3:17
  • OK, not the problem I thought you were having then... Next question: Does the remote site use the same IP addressing scheme as the local one? – Fabby Nov 30 '14 at 3:44
  • Yes, the addressing schemes are the same. I initially thought that might be a problem, but later assumed I was mistaken since Windows seems to have no issues with connectivity. – Matt Hamann Nov 30 '14 at 22:32
  • Hah! That's just luck and which adapter/protocol stack/... was installed first! ;-) Do you have ultimate control over (at least) one of the two addressing schemes??? – Fabby Nov 30 '14 at 22:40
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Seeing that this is a simple addressing scheme problem:

If you have control over both addressing schemes and you will be adding a lot of sites in the future: use the 10.A.B.C/24 addressing scheme where A is the country, B is the city and C is the local LAN... (think big!)

If you have control over only one of the addressing schemes (or will not be adding a lot of sites in the near future), have one use 192.168.dayofyourbirthday.0/8 (to make it sufficiently random that you will not have this problem again in the near future)

and all problems will be gone!

:-)

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  • 1
    I have control over both stacks, though one side is much simpler than the other. I'll change that one to a different scheme and try again shortly. – Matt Hamann Dec 1 '14 at 0:03
  • Once you've got more reputation on this site, upvote the answer! ;) – Fabby Dec 1 '14 at 20:06

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