Sunday, September 25, 2016

How to setup a Linksys WNDR3700v3 as a repeater.

Long house - Short Wifi

Living in a typical new orleans 'shotgun-layout' house, extending wifi to the back of the of the house has been an on going issue. Unfortunately the cable hook up is at the front of the house, and short of running 65' of coax, we needed something to boost wifi to the back of the house.

Our first solution involved an off the shelf wifi "extender", which we placed halfway between the front and back of the house, but our coverage remains spotty. Some of my peers recommended ditching the extended and using a router to boost wifi as a "repeater". I had an extra router layout around and, with a little bit of dark sorcery, I was able to setup my older router into a capable wifi booster. Specifically, I was able to successfully install DD-WRT firmware onto my router, and utilize its repeater capabilities.

(pic of both units)

Linksys WNDR3700v3

This article will be specific to the Linksys WNDR3700v3. I have written some steps a bit generically to potentially help those with a different routers; but unfortunately the steps involved vary so much depending on the specific router model and even down to which chip set the manufacture used. Results may vary.

What you will need:
-A Linksys WNDR3700v3 (this will be your secondary router)
-Another router (i.e. your host router) with internet.
-A laptop/desktop with an ethernet port
-An ethernet cable
-2 hours of your time
-Some patience (fail 3 times, succeed the fouth time)
-(optional) A second device with wifi capabilities. This will be handy to have a phone etc. to browse the net with for instructions while your laptop/desktop is tied up installing firmware on the router.
And lastly, at risk of sounding incompetent:
-the ability to sniff out when these instructions deviate from your situation. (In the end I needed mix-and-match 5 different walk-thoughs before I cobble together instructions for my hardware). This by no means a comprehensive guide; good luck :)

What you don't need:
-Physical access to the host router.
That's right, if all goes well, the host router will be none-the-wiser that a repeater has been setup. All setup is done with the secondary router. You could potentially setup a repeater off of your neighbor's wifi (so long as you know their wifi password) ;)


When dealing with routers I find that terminology is the biggest barrier. I'll make a small attempt to de-obfuscate. Please read this section or you will regret it.

"Repeater" vs. "Extender"
Manufactures are inconsistent or use misleading branding. All in all the two terms are interchangable. Either way, the concept is the same. A 'secondary router' will connect to the 'host router' via wifi. Devices connecting to either the host or secondary router via wifi will have internet access.
For this article I'll be using these terms in the following manner
* Extender - an off the shelf device intended solely for boosting signal. I won't talk about extenders in this article.
* Repeater - a normal router which has been configured to boost signal.

"Repeater Mode" vs. "Repeater Bridge Mode"
The folks over at DD-WFT provide the following definitions:
* Repeater Mode - This mode will extend wifi internet access to both routers, but the networks created by each router will exist on a separate subnet. The distinction here is that devices connected to the host router cannot communicate directly to devices on the secondary router. Effectively, this only impact you if you are LAN gaming or file sharing; otherwise this mode probably suits your needs. This is mode is easier to setup, and this is the mode I opted to use.
* Repeater Bridge Mode - This mode accomplishes signal boost, and both routers will exist on the same subnet (i.e. devices connected to different routers will behave as if all devices were connected to the same router). This mode is a bit more difficult to setup, and is not strictly covered in this article.
* Access Point - This is the default configuration for routers. This mode does no do any repeating.

While Repeater Bridge Mode is an ideal solution, it requires that your host router and secondary router have matching chip sets, and that both routers have supported DD-WRT firmware. In my instance, only my secondary router had supported DD-WRT firmware, so I fell back to using Repeater Mode. At the end of the day it accomplished my primary goal (getting better wifi coverage for my roommates); no biggie.

"Client" and "Client Bridge"
Without digging too deep into these modes, they are intended for people who want to run an ethernet cable between their routers, or for people who want to restrict client to connect to their routers via an ethernet cable (i.e. clients cannot connect to their router via wifi!). These setups only make sense for an office environment that has particular security restrictions. Most likely you'll want to stear clear of these modes. Just remember that "Client Bridge" is not the same as "Repeater Bridge".

Firmware from DD-WRT

DD-WRT is a community of people that make free opensource firmware, and is often cited as the best solution for most people (citation needed). Unfortunately their wikis are a bit rough around the edges, and sometimes even constradictory. It appears community support has wanned over the years. Nonetheless I had good luck with DD-WRT, at the very least will point you in the right direction.

If DD-WRT fails for you, you'll need to confide in an alternative source ( ).

As with any firmware shinanigans there a chance you can brick your router. How big a chance? I don't know. But you weren't using that old router for anything anyways, right? What do you have to lose! (Even if you do brick your router, there are large sections of the DD-WRT wikis dedicated to recovering a bricker router). You can do it!

(create image: brick with wifi antennas)

and without futher ado:

How to setup a Linksys WNDR3700v3 as a repeater.

The firmwawre that Linksys WNDR3700v3 ships with does not support any repeater modes. Especially for router that are 5-10 years old, there's a good change your router does not support a repeater mode.

1) Give your roomates a heads up that your messing around with the routers.
If all goes well, you won't even touch the host router, and they can go on watching netflix without interruption. You will only be touching the secondary router. Nonetheless hope for the best, set expectations for the worst.

2) Download your secondary router's manual.
Google it. Read it. Confirm that it doesn't already ship with a repeater mode. This may sound like an obvious step, I only include it beware of terminology soup. (They might call it "bridge mode" or something stupid).

3) Log into your secondary router's web interface.
Any device connected to a router can alter the router's configuration, so long as you know the address, username, and password. Unless you've explictly setup new values, username and password will still be the manufactures default. All routers have a default password. For Linksys WNDR3700 the default info is:
username: admin
password: password
Just open your web browser (e.g. chrome, safari, etc.) and type the address as the URL.

4) Update manufacture's firmware.
It's possible the manufactures has an updated firmware with what you need. Updating the manufactures firmware should be a one-click operation. With in the router's web interface, find a button to check for updates. Please double check and you may be able to skip this whole thing.
As of the date of this post the most recent Linksys firmware (v1.0.0.38_1.0.3.1) "Genie" does not support repeater modes.

5) Verify DD-WRT has a supported firmware for your router.
Pay attention to the exact 'version' of your device. I.e. a WNDR3700v2 is way different than a WNDR3700v3.
Of the 3 routers I own, only 1 was supported. If the router you picked to be your secondary router is not supported, but your host router is supported. Swap them out, and proceed with the other router as your secondary. Or maybe trade routers with your friends.

6) From the DD-WRT website, download the associated .chk file. Normally installing firmware is a 2 step process: install the .chk (aka 'the flash' or 'trailing build'), then install the .bin. (The .chk is a base firmware, and the .bin is a more advanced and updated firmware). I found that the .chk contained both 'Repeater Mode' and 'Repeater Bridge Mode', thus I skipped all instructions to install the .bin. If you need your router's USB/external harddrive support, you'll probably need to install the .bin.

Ok, you're finally ready to start messing with the firmware. Get excited!

7) Connect your laptop to the router via ethernet cable.
-During the course of these instructions, the router's wifi will be severed a few times during power cycles and reconfigurations. Connecting via an ethernet cable is *probably* mandatory; otherwise you risk firmware not being applied correctly. I hope you don't own a mac book air.

(create an image of a mac book air dongle with $999)

(optional) And just to be safe turn off your wifi adapter. This will ensure that all your browser's communications are going over the ethernet cable. This will reduce confusion and false positives in later steps. I know I've screamed Eureka a couple of times, only to realize I was connected to the wrong router.

8) Give your laptop a static IP on the same subnet as the secondary router.
At the moment your secondary router is probably on the subnet 192.168.1.X; thus set a manual static (i.e. non-changing) IP such as

(OSX pic)

9) Perform the voodoo that is the 30-30-30 Reset on the router. I had a stopwatch handy, otherwise counting to 30 gets really old really fast.

10) Log into your router's web interface (e.g.
If you have the latest firmware (v1.0.0.38_1.0.3.1) "Genie", you will be propted to answer one of three choices. This is good; this is an indication that the 30/30/30 reset was successful. At any point during the remaining instructions if you mess up, you can alway re-do the 30/30/30 and re-start from this step.

11) Install the .chk
Select the choice “I wanna do it myself”; click OK for the "... are you sure?" dialogs.
Click “Administration” button (on left of the screen) > click ‘router update’
Upload the .chk
It will warn you about installing an old version. Click OK.

(pic; blur sensitive information)

12) More voodoo
The loading bar will take about a minute to finish. After it has finished, wait an additional 5 minutes. Then perform another 30-30-30 reset.

13) Log back into the secondary router's web interface (e.g.
You should see a new "" interface.
These remaining instructions assume the following version is installed:
DD-WRT v24 SP2

14) Specify the host router's details.
Moment of truth.
Go to Wireless > Basic Settings
Here you should see 2 sections for Wireless Physical Interfaces, and 1 empty section for "Virtual Interfaces"

Pick one of the physician interfaces to use. The physical interfaces run on different frequencies; pick the freq that your devices most commonly connect to (probably the 2.4 GHz). You're welcome to try and apply these setting to both physical interfaces; I've only tried applying the settings to one interface.

For "Wireless mode" select "Repeater"
-If you do not see a value for Repeater, uh oh. You may need to install that .bin afterall; or your router might have a funky chip set. You may need to experiment with installing other versions of the DD-WRT firmware. Good luck.

For "Wireless Network Mode" select the same value as your host router. 90% odds are this value should be "Mixed". Otherwise, if you have web interace access to the host router, double check.

For "Wireless Network Name (SSID)" set to the SSID of the host network.

Leave "Sensitivity Range" as is.
Leave "Network Configuration" as "Bridged".

(pic; blur my mac address)

15) Add a virtual interface.
Click "Add" button
Populate "Virtual Network Name (SSID)". This will be the name of the wifi network that devices will connect to. This SSID cannot be the same as the host router's SSID.
Leave the other attributes as is.

At the bottom of the page, click the save button. (Do not click the Apply button yet.)

16) Specify passwords
Under the Wireless > Wireless Security tab
For the interface you selected in step 14:
For "Security Mode" select "WPA2 Personal"
For "WPA Shared Key" input the password for the Host router
Both the host router and the secondary router should have the same wifi password, and also the same security mode. This guide assumes the Host router has WPA Personal; otherwise, if you have access to the host router's web interface, log in and double check.
Repeat this for the virtual interface.

At the bottom of the page, click the save button. (Do not click the Apply button yet.)

17) Set the secondary routers on a different subnet.
By default, the virtual interface will be on the same subnet as the host router; ensure the virtual interface is on a different subnet.
Go to Setup > Basic Setup > Network Setup
For local IP address change the subnet (e.g.

18) Ease dynamic packet filtering firewall restrictions.
We'll remove some normal firewall restrictions, (as was recommended by one of the guides). If you know enough about firewalls, you may choose to leave these on. Otherwise:
Go to Security tab
- Uncheck "Block Anonymous LAN Requests"
- Leave "Filter Multicast" checked
- Uncheck "Filter WAN NAT Redirection"
- Uncheck "Filter IDENT (Port 113)"
Then select "SPI firewall" disabled. (It's important to do this last)

At the bottom of the page, click save button.
Now click Apply.

19) Verify secondary router has internet
If you have another device handy, connect to the secondary router's wifi, and verify you have internet connect.
If you are having issues, there are some additional tips at this link:

20) Clean up; get your laptop back to normal
* Re-enable your laptop's wifi adapter
* Re-set your laptop's IP to DHCP

21) Enjoy!

So, at the end of the day I replaced my out of the box extender with a router configured to be repeater. Was this time well spent? Did I actually see any performance improvements? Initial signs say yes. Though I don't have any before/after wifi heat maps to back it up, I'll be able to report back with my measurements in 'number of roommate complains per week'. Or, if push comes to shove, I can leap frog even further, and boost the secondary router's range with the new collecting dust extender.

Guides I referenced:

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