Automatic web proxy discovery

Discussion in 'Networking Issues' started by unionchurch, Sep 3, 2006.

  1. unionchurch

    unionchurch LI Guru Member


    I am trying to make plans to support automatic web proxy discovery in my small office network, since some of the client PCs are laptops that come and go. There will also be visiting laptops.

    I've been reading up on this. One strategy is to provide a web server with a virtual hostname of wpad.mydomain.tld, which the client web browser will seek out to download a proxy.pac file. For those who are as new to this as I am, WPAD stands for Web Proxy Automatic Discovery protocol.

    In another stategy, certain DHCP servers can provide instructions to aquire the proxy information to a client PC at the time the address lease is granted.

    I'm trying to figure out which if these is feasible with a SoHo-grade router controlling the LAN. The first choice above seems fairly straightforward, and it would be an easy matter to provide a webserver at However it's been my experience that most routers in the mdoest price range will not loop-back to the LAN if a client PC attempts to route a hostname on mydomain.tld, necessitating the insertion of a special line in the /etc/hosts file of the client PC. So, that sounds like the wpad.mydomain.tld comcept is no solution for SoHo-grade routers because visiting laptops will never be able to route to a local web host, thus their browsers will fail to find the proxy instructions.

    Your comments are most welcome.
  2. jgutz20

    jgutz20 Network Guru Member

    im not sure which router you have, but with a WRT54G and OpenWRT firmware, i made the proxy settings at the router level so everything was automatically routed to that.

    Another thing, all the proxy info is stored in the registry so you could create a Proxy On and Proxy Off reg key on the desktop and double click to apply these settings. This would let the users who are on the go get in and out quick
  3. unionchurch

    unionchurch LI Guru Member

    My present firewall/router is not a Linksys model, it is from a competing manufacturer. I am contemplating getting one soon for this small office network, but maybe something a little nicer than off-the-shelf retail. So the secret to getting the functionality you want (like looping back back into the LAN on the LAN's domain name) is to install 3rd-party firmware?
  4. unionchurch

    unionchurch LI Guru Member

    After I made that posting I went out and bought WRT54GL and flashed it with a copy of Tomato. It does indeed provide NAT loopback.
  5. HennieM

    HennieM Network Guru Member

    I take it the aim is to proxy/cache some of your web traffic? If so, maybe this will be helpful.

    I don't use my WRT's DHCP server, so I don't know if it allows you this:

    1) specify the default gateway to client machines (via DHCP) as the proxy server, and the second gateway as the router
    2) tell the router to only allow web traffic from the proxy server.

    The proxy server is aptly aliased to, so any client with "Auto-detect proxy" set should find it via one of the means you mentioned.

    I left out a few details, but hopefully you get the picture.
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