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HOWTO: Get WRT54G & WAP54G talking on WDS - reliably!

Discussion in 'Cisco/Linksys Wireless Routers' started by Hassan, Jul 25, 2005.

  1. Hassan

    Hassan Guest

    BACKGROUND:

    Until recently I had a star-shaped network with aging WAP11's as the core hardware. The central WAP11 was stuck up on a tall building in AP mode, with a bunch of client WAP11's talking to it. Even the backhaul link was a WAP11 client. It was a bit flaky at times, but usually worked satisfactorily.

    Since decent WAP11's aren't available anymore (I mean the ones with Amtel chips), I decided to upgrade to 802.11g with WRT54G's and WAP54G's. Naturally I assumed that these units would interact seamlessly. Not without some serious tweaking as I later discovered!

    I started by replacing the backhaul link with two WRT54G's (one on the NOC, the other wired to the central WAP11 AP). Both WRTs were installed with Sveasoft Alchemy 6.0-RC5a. I put them both in AP mode, talking to each other by WDS. When I was finished I had a 802.11g backhaul link consisting of two WDS WRT54G's wired to my old WAP11 network. For the moment it seemed ok, that is till I tried connecting a WAP54 wireless client to one of the WRT54G's!

    A WAP54 with mustdie firmware, in AP client mode, connected to one of the WRT54G's immediately, and seemed to be alright, till I tried downloading some large files across the wireless-g network. One or both of the WRT54G's would hang everytime, sometimes requiring a hard reset to return to action.

    This problem was completely solved by overclocking the WRT54G's to 216MHz. This is done by enabling telnet on the WRT54G, telnetting in, and typing the following at the prompt:

    nvram set clkfreq=216 <ENTER>
    nvram commit <ENTER>
    reboot <ENTER>

    I don't know why this hack solves the issue, but I can assure everyone that it does.

    ***

    Once I got the WRT54G's working stably even with fast transfers of big files across them, I encountered another problem, this time with the WAP54 AP clients. They were dropping their connections constantly. I tried upgrading them to the new 2.08 Linksys firmware (which claims to fix this problem) - with no luck. Not one to give up, I fiddled and tweaked till I found a much more elegant solution, which finally made everything rock solid: I enabled "Lazy WDS" On the WRT54G, and told the WAP54G to connect as either "Wireless Repeater" or "Wireless Bridge".

    I haven't tried WPA encryption yet but 128-bit WEP works fine.

    In any case I now have WRT54G's and WAP54Gs working together very nicely in a WDS network. The key tweaks I did are:

    - Installed Alchemy firmware on the WRT54G units
    - Installed Linksys 2.08 firmware on the WAP54G units
    - Overclocked the WRT54G's to 216MHz
    - Increased WRT54G XMIT power to 150mw
    - Configured WRT54G units to AP mode, with WDS & lazy WDS enabled
    - Configured WAP54's as Wireless Bridge connecting to the WRT54G MAC


    I get 400 - 700 kilobytes per second transfers when downloading files from my web server in the NOC, while I am behind one of the WAP54G's. This is going across 2 wireless hops like so:

    WEBSERVER<=LAN=>WRT54G<=WDS=>WRT54G<=WDS=>WAP54G<=LAN=>PC

    The old WAP11 AP is still in place, now wired to the WRT54G next to it, and still serving some of the WAP11 clients (the ones that haven't been upgraded to WAP54G's).

    CONCLUSION:

    Taking into consideration the above guidelines for configuring the WRT54G and WAP54G to work together in a WDS network, I can fully recommend them as a good combination in the kind of outdoor WISP setup I have.

    PS: We are going through a heat wave here - most days we have temps above 40 Deg C, no heat related problems so far!

    Regards,
    Hassan
     

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