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Cisco: OpenVPN and Cisco router

by Kliment Andreev
Reading Timee: 2 minutes

Recently, I bought a Cisco 3620 router with two Ethernet interfaces. I could’ve easily used one laptop running Linux/*BSD with two NICs, but I was planning to study IOS. My plan was to connect another laptop ( to my existing network. I also access my computers from outside using OpenVPN so I wanted to be able to access the new laptop with its internal IP. The image below briefly shows my wanted configuration.

First, I installed the router. I connected one cable from Eth0/0 to the Cisco switch where all computers have IP range. The second cable went from Eth0/1 interface on the router to another Netgear switch. I connected my laptop to this switch and assigned it a static IP of Next, I configured my Cisco router. This is a very simple configuration but it suits my needs.

router> ena
router# conf t
router(config)# int Eth0/0
router(config-if)# ip address
router(config-if)# no shut
router(config-if)# int Eth0/1
router(config-if)# ip address
router(config-if)# no shut
router(config-if)# router igrp 1
router(config-rou)# network
router(config-rou)# network
router(config-rou)# CTRL-Z

After this, I was able to ping both and from the router. But, when I tried to ping (Cisco 3600 router) from (FreeBSD server), I was getting no response. That’s because, there is no route to In order to make this happen, I have to do this on the FreeBSD box (

route add -net 

Which means, “If I have to reach network, use as a gateway, not the default one.” In order this change to be permanent, I added the following in /etc/rc.conf:

# Static route to

You can check your route with “netstat -rn” on FreeBSD and Mac OS X and with “route print” on Windows.

Because I made this change on which is a default router for all my computers on subnet, I don’t have to go to each one of them and change the router settings. So, when I do ping on a computer with IP and as a gateway, the gateway (FreeBSD box) simply forwards these packets to (Cisco 3600 router).
I went back to computer and I confirmed that I can ping There is no need to change routes on this network, because they use as a gateway which knows how to route to Mind that network is using two routes. One for the outside world ( and one to access network.
Once I confirmed that I can route between two networks, I went back to Cisco router and added the following command:

router(config)# ip route 

which is very similar to route add -net. It means, use as a gateway to reach network.
I also had to add the following line in openvpn.conf on the OpenVPN server (

push "route"
# Line below was added 
push "route" 

Once this was done, I was able to access any device on my network.

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