Edgerouter IPsec tunnel to Fritzbox

So, I have an EdgeRouter Lite in Singapore (Starhub) and a FritzBox in Belgium (EDPnet).

This is mostly stuff that I have found from several articles, mostly from here.

ERL: eth0 is WAN, eth1 ( and eth2 (unused, not VPN’ed) are LAN

This is the FritzBox config (go to VPN and them Import a config) fritzvpn.cfg:

vpncfg {
        connections {
                enabled = yes;
                conn_type = conntype_lan;
                name = "VPN Yeri";
                always_renew = yes;
                reject_not_encrypted = no;
                dont_filter_netbios = yes;
                localip =;
                local_virtualip =;
                remoteip =;
                remote_virtualip =;
                remotehostname = "erl.yeri.be";
                localid {
                        fqdn = "fritz.yeri.be";
                remoteid {
                        fqdn = "erl.yeri.be";
                mode = phase1_mode_idp;
                phase1ss = "all/all/all";
                keytype = connkeytype_pre_shared;
                key = "SOMEPASSWORD";
                cert_do_server_auth = no;
                use_nat_t = yes;
                use_xauth = no;
                use_cfgmode = no;
                phase2localid {
                        ipnet {
                                ipaddr =;
                                mask =;
                phase2remoteid {
                        ipnet {
                                ipaddr =;
                                mask =;
                phase2ss = "esp-all-all/ah-none/comp-all/pfs";
                accesslist = "permit ip any";
        ike_forward_rules = "udp", 

Be sure to modify the password, local (Fritz) and remote (ERL) LAN and edit the local and remote fqdn.

This is the ERL config (via ssh, you’ll need to set this:

yeri@sg-erl# show vpn ipsec 
 auto-update 60
 auto-firewall-nat-exclude enable
 esp-group FOO0 {
     proposal 1 {
         encryption aes256
         hash sha1
 ike-group FOO0 {
     dead-peer-detection {
         action restart
         interval 60
         timeout 60
     lifetime 3600
     proposal 1 {
         dh-group 2
         encryption aes256
         hash sha1
 ipsec-interfaces {
     interface eth0
 nat-networks {
     allowed-network {
 nat-traversal enable
 site-to-site {
     peer fritz.yeri.be {
         authentication {
             mode pre-shared-secret
             pre-shared-secret SOMEPASSWORD
         connection-type initiate
         description "VPN to fritz.yeri.be"
         ike-group FOO0
         local-address erl.yeri.be
         tunnel 1 {
             esp-group FOO0
             local {
             remote {


yeri@sg:~$ show vpn ipsec status
IPSec Process Running PID: 20140

1 Active IPsec Tunnels

IPsec Interfaces :
        eth0    (no IP on interface statically configured as local-address for any VPN peer)
yeri@sg:~$ show vpn ipsec sa
peer-be.yeri.be-tunnel-1: #9, ESTABLISHED, IKEv1, 85a2d010ada73113:ca439c40ac3bca06
  local  'erl.yeri.be' @ 116.87.x.y
  remote 'fritz.yeri.be' @ 109.236.x.y
  established 1592s ago, reauth in 1333s
  peer-fritz.yeri.be-tunnel-1: #1, INSTALLED, TUNNEL, ESP:AES_CBC-256/HMAC_SHA1_96/MODP_1024
    installed 1592 ago, rekeying in 1200s, expires in 2009s
    in  c0bb652e, 1038032 bytes, 10726 packets,     0s ago
    out 8d5df3f5, 532685 bytes,  6062 packets,     0s ago

I haven’t really figured out what no IP on interface statically configured as local-address for any VPN peer means yet though.

Next up: VLANs

OpenVPN packet drops

I recently started to notice following error messages on my openVPN server.

ovpn-server[6306]: vpn.rootspirit.com/85.234.x.y:62068 MULTI: packet dropped due to output saturation (multi_process_incoming_tun)

This basically means that the TUN or TAP interface is making more packets than the real (TCP) interface can handle.

As I need to run OpenVPN using the TCP protocol (instead of the faster UDP protocol; as UDP is often blocked in networks I use my VPN in) I experimented by increasing the tcp-queue-limit. The default is 64, and I’ve set it to 256. So far, everything still seems to be working fine (but more packets will be queued before being dropped by OpenVPN, requiring less retransmissions).

Add this to the OpenVPN server config:

tcp-queue-limit 256

And restart the daemon.

OpenVPN & Windows 7

There’s a great GUI out for OpenVPN & Windows, located here.

However, this GUI includes an old OpenVPN, that is no longer compatible with Windows 7 and Windows Vista.

The TUN/TAP driver will be blocked due to compatibility issues, and when trying to connect to a VPN, you’ll get an error along the lines of:

All TAP-Win32 adapters on this system are currently in use

The simplest fix, is to install the GUI package (including the old OpenVPN binaries), and reinstall OpenVPN afterwards.

You can find the latest OpenVPN binaries here and the latest version, when writing this post here.

This will overwrite the old files and update the driver with a Windows 7 compatible driver.

Try to connect now, everything should work like a charm. ūüôā


OpenVPN Linux + Mac howto

A short howto, as I was unable to find any clear ones on the net.

I’m using Mac OS X (Leopard) as client, and a Gentoo server as server/host.

I both tried Viscosity and Tunnelblick on my Mac as OpenVPN software, and Viscosity is probably somewhat easier to configure (using the GUI), it was shareware. So I ended up using Tunnelblick and it seems to be doing its job quite well.

First of all, make sure Gentoo is set up and working as intended. I used my home router as VPN server (having both eth0 and eth1 (= ppp0).

Using this howto, you’ll be able to get the server up and running.

Besides the installation, and perhaps (config) file locations it should be pretty similar on other Linux distros.

As I have dnsmasq running on my server (taking care of DNS) I added the following to the server.conf:

push "dhcp-option DNS"
push "redirect-gateway def1"
client-config-dir ccd

Don’t forget to allow DNS requests over tun0 interface in dnsmasq.conf.

The first line tells the server to hand out as DNS server to its connecting clients ( being the internal eth0 IP of my server).

The 2nd line, tells all clients to route ALL of their traffic through the VPN. I used the VPN to access a website that allowed only Belgian IPs, and I was in The Netherlands at the time I had to access the site (Skynet’s Rock Werchter stream). So I connected through my server at home.

And the 3rd and 4th line are needed if the client access the VPN is on a private IP subnet (like being connected on a WiFi router, using IP 192.168.178.x).

You’ll have to add, in the client-config directory a file per username connecting to the VPN with something similar to this:


I’m not entirely sure if you can add multiple iroutes; something I’ll have to figure out when being on a different network.

This is what my client config looks like (vpn-server-name.conf, located in ~/Library/openvpn/):

dev tun
proto udp
remote home.tiete.be 9000
resolv-retry infinite
tun-mtu 1500
tun-mtu-extra 32
mssfix 1200
ca "ca.crt"
cert "yeri.crt"
key "yeri.key"
tls-auth "ta.key" 1
verb 3

Yeri being my username. Don’t forget to download and add the ca.crt, user.crt, user.key (located in /usr/share/openvpn/easy-rsa/keys/) and ta.key (located in /etc/openvpn/) you’ve created on the server.

If your client asks for “directions”, pick 1.

Start up server and client software.

Hitting connect in Tunnelblick should connect you to the VPN server, and (in my case) giving me an IP similar to You can check this using “ifconfig” in Terminal.


tun0: flags=8851 mtu 1500
	inet --> netmask 0xffffffff
	open (pid 20551)


tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:  P-t-P:  Mask:
RX packets:407595 errors:0 dropped:0 overruns:0 frame:0
TX packets:574351 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:27473209 (26.2 MiB)  TX bytes:603524377 (575.5 MiB)

Don’t forget; when using “tun” as driver, your gateway/VPN server will always have the IP ending on .1 (e.g.:

Now, if you want to route all traffic throug the VPN, like I did, you’ll have to change some stuff in iptables (as the server is also acting as my home router, I already did have a few rules in it).

Allow all traffic through tun0 interface:

iptables -A OUTPUT -o tun0 -j ACCEPT
iptables -A INPUT -i tun0 -j ACCEPT

Allow traffic through the external port 9000 (UDP):

iptables -A INPUT -i ppp0 -p udp -m udp --dport 9000 -j ACCEPT

Enable forwarding and NAT:

iptables -A FORWARD -s -i tun0 -j ACCEPT
iptables -A FORWARD -d -i ppp0 -j ACCEPT
iptables -A POSTROUTING -o ppp0 -j MASQUERADE

And lastly, as I have Squid running on my server, I want to transparently forward all port 80 requests to the Squid server running on port 8080:

iptables -t nat -A PREROUTING -i tun0 -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 8080

That’s about it. You should have a running VPN from your current location to your VPN server. And you’re able to use it as a gateway.

You can always traceroute/tracepath to your VPN server ( It should only find one hop.