Tag Archives: openvpn

DNS Conditional Forwarding – dnsmasq

Why would I want to use Conditional Forwarding?

In my case, my local dns server has entries for local hostnames such as m2n.ion.lan, mongo.ion.lan, and tux.ion.lan. If I am using the vpn dns, then these address lookups would fail. By using Conditional Forwarding I can do all lookups locally, except for ones that match the remote top level domain (example.local). Anything that matches example.local would be forwarded to the remote dns server.


  1. Connect to remote vpn server and use local DNS server
  2. Ping server.remote.local (remote FQDN) – fail
  3. Ping server.ion.lan (local FQDN) – success

Of course the remote ping fails because the local DNS server knows nothing about the remote domain. If I was to configure my machine to use the remote DNS server the opposite would happen. I would be able to ping server.remote.local, but a ping to server.ion.lan would fail.

Solution: Use dnsmasq with conditional forwarding to forward *.work.local requests to the remote dns server.

1. Install dnsmasq using your local package manager

2. Edit /etc/dnsmasq.conf

# Tells dnsmasq to forward anything with the domain of remote.local to dns server

# Listen to requests only coming from the local machine

# Do not cache anything
# A decent dns server will already cache for your local network

3. Edit /etc/resolv.conf

# Local LAN Domain
domain ion.lan

# local dnsmasq server

# Your main dns server (dnsmasq will forward all requests to this server)

4. Start dnsmasq

5. Test – ping a local server and remote server using the FQDN

All dns requests will be forwarded to except any matching *.remote.local. server.remote.local will be forwarded to

OpenVPN Client – DNS Script

The OpenVPN server can pass DNS servers and a domain name to the client. This gives the benefit of using the remote dns servers for local hostname lookups.

Finding a good script that worked to do this provide difficult…

In server.conf add:

push "dhcp-option DOMAIN ion.lan"
push "dhcp-option DNS"

Then save this script on the client in same location as the client config


case "$1" in
	    mv /etc/resolv.conf /etc/resolv.conf.bak

		echo "# Generated by OpenVPN Client UP Script" > /etc/resolv.conf
		for opt in ${!foreign_option_*};
	        echo ${!opt} | sed -e 's/dhcp-option DOMAIN/domain/g' -e 's/dhcp-option DNS/nameserver/g' >> /etc/resolv.conf
        mv /etc/resolv.conf.bak /etc/resolv.conf
        echo "Pass either UP or DOWN"

In the client.conf add

script-security 2

up "./vpn_dns_update.sh up"
down "./vpn_dns_update.sh down"

Now connect and check /etc/resolv.conf to see if the VPN nameserver and domain is listed.