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I have two computers connected with VPN, and some virtual machines on each. I want everything to see each other (that is basically 4 different networked machines). What I've not managed so far is that a computer on the one end to be visible to the other end. In tracert terms:

192.168.78.42>tracert 192.168.69.18
Tracing route to WIN-2K8R2 [192.168.69.18]
over a maximum of 30 hops:
  1    <1 ms    <1 ms    <1 ms  192.168.78.17
  2     *        *        *     Request timed out.
  3   217 ms    78 ms    78 ms  WIN-2K8R2 [192.168.69.18]
Trace complete.
192.168.78.42>tracert 192.168.69.112
Tracing route to 192.168.69.112 over a maximum of 30 hops
  1    <1 ms    <1 ms    <1 ms  192.168.78.17
  2   333 ms     *      337 ms  WIN-2K8R2 [192.168.86.22]
  3/4/5     *        *        *     Request timed out.
  6  ^C
192.168.69.18>tracert 192.168.69.112
Tracing route to 192.168.69.112 over a maximum of 30 hops
  1    <1 ms    <1 ms    <1 ms  192.168.69.112
Trace complete.
192.168.69.112>tracert 192.168.78.42
Tracing route to 192.168.78.42 over a maximum of 30 hops
  1     1 ms     *       <1 ms  192.168.69.18
  2    79 ms    77 ms    80 ms  192.168.86.21
  3    80 ms    77 ms    81 ms  192.168.78.42
Trace complete.

Note: the 4 machines are 192.168.69.112 (winXP), 192.168.69.18=192.168.86.22 (win2K8R2), 192.168.86.21=192.168.78.17 (Linux), 192.168.78.42 (win2K3).
The VPN is a TAP openvpn connection between 192.168.86.21 and 192.168.86.22.
I would say that the problem is in the win2K8 machine, but Windows networking is my weak point.

Edit@2011.11.26: Since I use VPN, there is a possible workaround to connect the winXP with win2K3 by making a VPN connection from the winXP machine to the Linux VPN server. But the original problem, namely why the win2K8R2 does not forward packages, remains unsolved.


The routing tables (without broadcast, etc entries):
winXP

Network Destination        Netmask          Gateway       Interface  Metric
      0.0.0.0          0.0.0.0         10.0.3.2       10.0.3.15   20
     10.0.3.0    255.255.255.0        10.0.3.15       10.0.3.15   20
    10.0.3.15  255.255.255.255        127.0.0.1       127.0.0.1   20
 10.255.255.255  255.255.255.255        10.0.3.15       10.0.3.15     20
    127.0.0.0        255.0.0.0        127.0.0.1       127.0.0.1   1
  192.168.0.0    255.255.255.0    192.168.0.112   192.168.0.112   20
  192.168.0.112  255.255.255.255        127.0.0.1       127.0.0.1     20
  192.168.0.255  255.255.255.255    192.168.0.112   192.168.0.112     20
 192.168.69.0    255.255.255.0   192.168.69.112  192.168.69.112   20
 192.168.69.112  255.255.255.255        127.0.0.1       127.0.0.1     20
 192.168.69.255  255.255.255.255   192.168.69.112  192.168.69.112     20
 192.168.78.0    255.255.255.0    192.168.69.18  192.168.69.112   1
...
Default Gateway:          10.0.3.2
===========================================================================
Persistent Routes:
Network Address          Netmask  Gateway Address  Metric
   192.168.78.0    255.255.255.0    192.168.69.18       1

win 2K8R2

Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0      192.168.0.1     192.168.0.17     20
      192.168.0.0    255.255.255.0         On-link      192.168.0.17    276
     192.168.0.17  255.255.255.255         On-link      192.168.0.17    276
    192.168.0.255  255.255.255.255         On-link      192.168.0.17    276
     192.168.69.0    255.255.255.0         On-link     192.168.69.18    276
    192.168.69.18  255.255.255.255         On-link     192.168.69.18    276
   192.168.69.112  255.255.255.255         On-link     192.168.69.18     21
   192.168.69.255  255.255.255.255         On-link     192.168.69.18    276
     192.168.78.0    255.255.255.0    192.168.86.21    192.168.86.22     31
    192.168.86.20  255.255.255.252         On-link     192.168.86.22    286
    192.168.86.22  255.255.255.255         On-link     192.168.86.22    286
    192.168.86.23  255.255.255.255         On-link     192.168.86.22    286
...
===========================================================================
Persistent Routes:
  Network Address          Netmask  Gateway Address  Metric
     192.168.78.0    255.255.255.0    192.168.86.21       1
   192.168.69.112  255.255.255.255    192.168.69.18       1

Linux

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         *               0.0.0.0         U     0      0        0 ppp0
10.0.0.1        *               255.255.255.255 UH    0      0        0 ppp0
192.168.69.0    192.168.86.22   255.255.255.0   UG    0      0        0 tap1
192.168.75.0    192.168.86.22   255.255.255.0   UG    0      0        0 tap1
192.168.75.0    192.168.86.22   255.255.255.0   UG    0      0        0 ppp0
192.168.76.0    *               255.255.255.0   U     0      0        0 eth0
192.168.78.0    *               255.255.255.0   U     0      0        0 vboxnet0
192.168.85.0    *               255.255.255.0   U     0      0        0 vboxnet1
192.168.86.16   *               255.255.255.252 U     0      0        0 tap0
192.168.86.20   *               255.255.255.252 U     0      0        0 tap1
192.168.186.24  *               255.255.255.252 U     0      0        0 tap2

win2K3

Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0    192.168.78.17    192.168.78.42     10
        127.0.0.0        255.0.0.0        127.0.0.1        127.0.0.1      1
     192.168.78.0    255.255.255.0    192.168.78.42    192.168.78.42     10
    192.168.78.42  255.255.255.255        127.0.0.1        127.0.0.1     10
   192.168.78.255  255.255.255.255    192.168.78.42    192.168.78.42     10
     192.168.85.0    255.255.255.0    192.168.85.42    192.168.85.42     10
...
Default Gateway:     192.168.78.17
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what type of vpn ? whats the gateway ? what are the routing tables ? –  Sirex Nov 20 '11 at 0:36
    
@Sirex: I use a static key openvpn 2.2.0 (some Debian build), with the windows client 2.2.1, and 192.168.86.21/255.255.255.252 addresses. I can't provide routing table right now, but my point is that the echo request as well as an RDP connection works in one direction, but fails on the other. Since echo reply is works in the other way, I suppose, that the routing table should be fine. I could implement this behavior of –  user101531 Nov 20 '11 at 2:32
    
I meant: ... this behavior of the win2K8R2 machine with iptables manipulating the FORWARD chain, but that is a really non-standard setting. (Sorry, patchy internet) –  user101531 Nov 20 '11 at 2:43
1  
if you can provide a diagram of network, that would be much better and very easy to understand the network for everyone here. –  Farhan Nov 26 '11 at 14:14

1 Answer 1

but my point is that the echo request as well as an RDP connection works in one direction, but fails on the other. Since echo reply is works in the other way, I suppose, that the routing table should be fine

Routes should be in place to each network on each host. I've seen cases where a route is installed in one machine and not other and what you described before is exactly what happened.

Add the route with the correct gateway that can reach the other netblock

Windows Example = route add -p 192.168.X.X/24 gw 192.168.X.X
Linux Example = route add -net 192.168.X.X/24 192.168.X.X

-p makes it persistent on reboot for windows. To make the route peristent through reboot for Linux you'll have to add the route the static-routes file.

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