From DD-WRT Wiki

Revision as of 15:59, 27 December 2006

Introduction

This How-To provides step-by-step instructions for creating a Universal Wireless Repeater appliance: a device that you can place anywhere and it will wirelessly repeat the strongest signal, onto another wireless network (with or without security). This functionality is also known as Wireless Client Bridge, or Range Expander. Unlike WDS, once you have this appliance setup, it will work with any open network.

Architecturally the Wireless router connects to the other Wireless router as a client, getting a single IP address via DHCP. Effectively the SSID network you are connecting to, becomes your ISP. This is why you must allocate your own IP address space, which must be different from the network address you get from the router your DDWRT router connects to.

For example:

In a given neighborhood, there are 3 open access wireless networks, jojo, linksys and internetmad. Using a site survey, you see that jojo has the best signal quality and seems to have plenty of bandwidth. You configure your UWR SSID to be in the network jojo. If you reboot the DDWRT router it will receive an IP address automatically from jojo. Let's say jojo is using 192.168.1.0/24, and your DDWRT router receives the address 192.168.1.139. You have previously configured your repeater network to use 172.16.100.0/24. When you configure your laptop, you associate with the SSID "repeater" and you receive the address 172.16.101.100 via DHCP. As far as your laptop is concerned you are talking to repeater. As far as repeater is concerned, it's gateway is "jojo" and jojo probably has another gateway via cable modem or DSL.

Prerequisites

• Know how to use and access Web Interface
• Know how to flash your device.

It takes me just a couple minutes to follow these instructions (but I've done this before).

Instructions

1. Install DD-WRT v24 beta(v23 will not work).

• Build 2006-0911 is known to be stable for repeater mode. Users also report success with newer builds like 2006-1221.
• Keep ethernet cable connected for these instructions (to have connectivity across wireless network changes).

2. Go to tab "Setup", sub-tab "Basic Setup":

• Change "local IP address" to a unique subnet (different than device you wish to repeat), such as 192.168.69.1.
• Save settings.

3. Go to tab "Security", sub-tab "Firewall":

• Disable all check boxes and set firewall to "disable".
• Save settings.

4. Go to tab "Wireless", sub-tabe "Basic Settings":

• Set Wireless Mode to "Repeater"
• Click on "Add" under Virtual Interfaces, and enter an SSID (such as "repeater") and set "Wireless Network Name (SSID)" to the network you wish to repeat (and AP Isolation is "disabled" and Network Configuration is "Bridged"). If you want the source network (the one your repeating) to be dynamically acquired, see steps below.
• Optional: Set Wireless Channel to "Auto" (or your preferred channel), and set Sensitivy Range to "0" for performance enhancements.
• Click "Save Settings".

5. To repeat any network dynamically (make this a universal wireless repeater), the following will make the repeater connect to the first available SSID:

• Go to tab "Administration", subtab "Command".
• Copy and paste the following into the edit box:

nvram set wl_ssid=""
nvram commit

• Click the Save Startup button.

• Note: this will not automatically repeat secure/encrypted networks. If your source network uses WEP or WPK, enter the ssid under the Physical Interface in step 4 instead, and proceed to the next step.

6. You may use security (WEP, WPA, etc) in repeater mode. An example application of this would be to make the repeated network private (for your use only).

• Go to tab "Wireless", sub-tab "Wireless Security".
• Setup WEP (or other security) under virtual interface.
• Configure your client/computer to use the same security.

• Notice in the screenshot above you may also configure security for the physical interface (source) network if you wish to repeat a secure network. In the example this is disabled. If you enable this, the dynamic repeating functionality may not work (since you're hard configuring the source network).
• Note: At this time, only one interface can have security - not both simultaneously. See "Known Issues" below.

7. The first time you connect to the repeater (wirelessly), or after disconnect, you may need to perform a "repair wireless network connection". For example, in XP, right click on the wireless icon and select "Repair".

Optimizations

8. If you wish to dynamically repeat the STRONGEST signal (a more sophisticated, robust and configurable replacement version of #5 above) please read the AutoAP Wiki Article.

AutoAP is a script that continuously scans for open wifi connections, tests them for validity, and connects to the strongest signal. If the connection is lost, the script scans again and finds the strongest valid signal again, and maintains a continuous connection to the internet in a mobile or portable environment. The script paremeters are highly configurable, including ability to configure secure connections.

9. For optional repeater performance enhancements:

• Go to tab "Administration", subtab "Management". Enter the following values under 'IP Filter Settings':

  TCP Timeout (s): 90
  UDP Timeout (s): 90

• Go to administration tab, subtab "Command": Edit the existing command text and paste the following into the edit box before the existing commands:

  echo '600 1800 120 60 120 120 10 60 30 120' > /proc/sys/net/ipv4/ip_conntrack_tcp_timeouts

• Go to tab "Wireless", subtab "Advanced Settings". Set "Beacon Interval" to a lower value (like 50 or 75).
• Go to tab "Administration" and subtab "Management" and set overclocking frequency to a higher value than default.
• Go to tab "Wireless" and subtab "Advanced" and boost xmit power to higher than default.

Troubleshooting

• If you are having problems getting repeater mode working, first setup Client Mode or Client-Bridged Mode as a test. Once you have client mode working, then switch to repeater mode (keeping all your other settings) - verify its still working, and then add the virtual interface(s).
• The first time you connect to the repeater (wirelessly), or after disconnect, you may need to perform a "repair wireless network connection". For example, in XP, right click on the wireless icon and select "Repair".
• See Known Issues below.

Known Issues

• Bugtracker has an entry "Cannot use two SSIDs with different encryption settings at the same time." For repeater mode, this may mean you cannot have security on the physical and virtual interface at the same time for some builds. See bugtracker entry.

• Build 0911 and earlier: you can't ping the devices (peers) on the virtual interface as reported here.

• Build 0911: some users report repeater mode prematurely drops the client, especially in challenging environments. Not everyone sees this. If this is an issue for you, you may use a workaround router script ("dhcp_kick.sh"). dhcp_kick.sh loops, pinging the gateway. If gateway down, script sends a signal to udhcpc (on the router) to force renew - and as a last resort it restarts udhcpc.

Links

Your testing results and enhancements are appreciated:

• For contributions to UWR: http://www.dd-wrt.com/phpBB2/viewtopic.php?p=42375
• For contributions to AutoAP: http://www.dd-wrt.com/phpBB2/viewtopic.php?t=6575