Knowledge Base

giffgaffer's guide to connect a 3G Modem On DD-WRT

Started by: francisuk
On: 11/03/2012 | 20:34
Replies: 2

by: francisuk
on: 11/03/2012 | 20:34 edited: 28/05/2016 | 16:13

giffgaffer's guide to connect a 3G Modem On DD-WRT


This is a guide to setting up your DD-WRT modem for giffgaff. The instructions mentioned are based upon NETGEAR WDR3400 V1. There will also be slight different variations according to DD-WRT firmware.


First, See if your Router is compatible, You can do this in lots of ways.


1) Router Database


2) DD-WRT Forums (Search your Model Number)


Then upgrade to the latest DD-WRT builds (Sorry FTP is only available)


Once you have flash to DD-WRT, Follow the steps below;


Log in with the username and password in the pop-up window:



WAN Setup -
Connection Type: 3G/UMTS/4G/LTE

3G Connection
Username: giffgaff
Password: password
Dial String: *99#
Connection type: 3G first on error 2G
Force reconnect: you decide!

Network Setup -
Start IP Address: 10
Maximum DHCP Users: 9


Hit Save


Go to Wireless tab at the top, You will see something like...

Physical Interface wl0 - SSID [dd-wrt] HWAddr [C4:3D:XX:XX:XX:XX]

Wireless Mode: AP
Wireless Network Name (SSID): ANY WIRELESS NAME YOU WONT E.G giffgaff 3G
Wireless Channel: Auto
Channel Width: Auto


Hit Save


Go to Wireless Security at the top

Security Mode: WPA2 Personal
WPA Algorithms: AES+TKIP


Hit Save, Go to Services at the top


Static Leases (Skip if you dont wont to reserve IP addresses)
Import you PC, Laptop or any mac address you would like to reserve (good for \\ SAMBA, Printer sharing etc


Hit Save, Apply settings



Once rebooted unplug the DD-WRT device and put in your 3G dongle


You should see WAN IP: 10.x.x.x


Latestly, Go to Administration then Commands and import this info the white box


LAN_IP=`nvram get lan_ipaddr`
LAN_NET=$LAN_IP/`nvram get lan_netmask`

iptables -t nat -A PREROUTING -i br0 -s $LAN_NET -d $LAN_NET -p tcp --dport 80 -j ACCEPT
iptables -t nat -A PREROUTING -i br0 -s ! $PROXY_IP -p tcp --dport 80 -j DNAT --to $PROXY_IP:$PROXY_PORT
iptables -t nat -I POSTROUTING -o br0 -s $LAN_NET -d $PROXY_IP -p tcp -j SNAT --to $LAN_IP
iptables -I FORWARD -i br0 -o br0 -s $LAN_NET -d $PROXY_IP -p tcp --dport $PROXY_PORT -j ACCEPT


Hit Save Firewall


and reboot and power off and on again.


Enjoy Smiley Happy

Get a free giffgaff Sim
Message 1 of 3
by: abubaker1975
on: 20/10/2015 | 17:18

Hi There


I have 4G Modem and flashed Netgear R7000 router with DD-WRT. I am unable to connect my 4G modem to my router. I tried to follow your instructions but I don't have Connection Type: 3G/UMTS/4G/LTE option in the dropdown menu. Only time I am able to connect to the internet is when I chose the option Mobile Broadband option in the drop down menu but then I don't have WAN connection for my VPN


Need your urgent help.



Message 2 of 3
by: cass905
on: 21/10/2015 | 16:56
What a great guide very useful information thank you and well done
Message 3 of 3