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I am trying to solve a problem I have with a Cisco VPN. Basically, when I work from home, I now use Remote Desktop through Hamachi to work directly with my computer at the office. Hamachi works fine for this, because no ports need to be opened in the company's firewall. Only problem is, Hamachi connection is often too slow and because of this, I am now working on my home PC and using Dropbox to get all the changes synced almost in real time on my work PC. This is OK, but unfortunately there still is something for which I need to RDP to the work PC... which is what I'd like to avoid. Every now and then I need to access some servers through a VPN which I can access from my work PC, but not for home. Is there anyway I could access the second VPN (a Cisco) from my home PC, through the Hamachi connection to the work PC?

Say - Hamachi assigns, for example, the IP 5.1.1.1 to my HOME PC - Hamachi assigns, for example, the IP 5.1.1.2 to my WORK PC - Cisco VPN assigns the IP 10.0.1.1 to my WORK PC - One compute I want to access through the Cisco VPN has IP 10.0.0.20

How do I proceed? I have tried with

route add 10.0.0.0 mask 255.255.255.0 5.1.1.2

on my HOME PC, but nothing changes. I still can't ping any of the 10.0.0.x. Any ideas?

Thanks in advance!

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3 Answers 3

Adding the route 10.0.0.0 to 5.1.1.2 simply forwards the packets over a specified interface. The machine on the other side of that interface needs to know what to do with the packets it receives.

So, on your middle machine, it needs to know that when it gets a request FROM 5.1.1.1 asking for 10.0.0.20 to send it over the VPN. By default, Windows machines will just drop the packet.

To fix this, your windows machine in the middle needs to act as a(nother) router. The simplest way of doing this in Windows XP is to enable IP Forwarding, as noted in this KB.

HOWEVER - I have very serious doubts that what you're trying to do will work with just IP forwarding. What you're wanting to do is connect three disparate networks over two node-to-node VPNs, different subnets and consumer level software. This is not an easy task to do, and don't be surprised if there's no (easy) way you can get it working. Plus, I'm not sure your work would be too pleased if they knew you were doing this (otherwise they would just give you a VPN client for your home as well).

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Hi, many thanks for the quick response. At work all is fine, they of course know what I do from home, no problem with that. I will likely ask our NA to set up a VPN access from my home computer, but I also want to see if what I described is possible, to learn as well. I have changed that setting on the work computer, restarted, but nothing has changed. Do I have to do something else on the work PC? Thanks! –  Vito Botta Aug 29 '09 at 12:37

You could try using OpenVPN instead of Hamachi.

With OpenVPN, you can:

tunnel any IP subnetwork or virtual ethernet adapter over a single UDP or TCP port,

configure a scalable, load-balanced VPN server farm using one or more machines which can handle thousands of dynamic connections from incoming VPN clients,

use all of the encryption, authentication, and certification features of the OpenSSL library to protect your private network traffic as it transits the internet,

use any cipher, key size, or HMAC digest (for datagram integrity checking) supported by the OpenSSL library,

choose between static-key based conventional encryption or certificate-based public key encryption,

use static, pre-shared keys or TLS-based dynamic key exchange,

use real-time adaptive link compression and traffic-shaping to manage link bandwidth utilization,

tunnel networks whose public endpoints are dynamic such as DHCP or dial-in clients,

tunnel networks through connection-oriented stateful firewalls without having to use explicit firewall rules,

tunnel networks over NAT,

create secure ethernet bridges using virtual tap devices, and

control OpenVPN using a GUI on Windows or Mac OS X.

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It is also incredibly more complicated than Hamachi. –  Reinis I. Oct 5 '09 at 20:31
    
yeah, i agree although there exists a openVPN GUI to make it easier. –  djangofan Oct 6 '09 at 21:25

suggest logmein if you just need remote desktop every so often

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