Simple Redundant Wireless Link?

little otter hath wroth:

No flying dinosaurs yet, but lots of pigeons and pigeon droppings. Incidentally, that's the way I test people for wireless experience. If they don't know what solvent cleans up pigeon droppings, they've never worked on an urban radio system.

Instant bridging loop. As drawn, there's no way to keep a packet from going round and round and round the loop formed between switches. You can simulate the problem by replacing the two wireless links with just some CAT5 between the two ethernet switches. It won't take long to see the problem by watching the flashing lights (or using SNMP monitoring if the boxes are managed switches).

However, it will work if your switches can do STP (spanning tree protocol), preferably Fast STP also known as 802.1w or MSTP (multiple STP) also known as 802.1S or preferably 802.1Q. See:

Also:

Gee thanks. You give me a specialized problem and don't let me suggest complicated and specialized hardware and protocols. That's no fun, so I'll just ignore that restriction.

You can do load balancing between two bridged paths using VLAN's and STP. See:

I've never tried doing this, but it looks like it will work. (Translation: I don't really understand how it works until I've tried it). The benefit is that you get to use both wireless links simultaneously for double the thruput. The price is complexity.

Any pair of ethernet switches that will do one of the numerous flavors of STP.

You can also do fail over using routers, but that will complicate your IP layout. RIP2 (router information protocol) can also be used to switch paths. Details on request.

One is usually sufficient.

Incidentally, make sure you have some physical isolation between the pairs of antennas. That means that you should not visually see the "redundant" antenna across the 60 yard path. Cheapo wi-fi radios do not have very good overload characteristics and are quite susceptible to overload and interference from nearby off channel xmitters.

Jeff, did you work on the free wireless project in SC with Eric Kellogg?

dualdflipflop hath wroth:

Nope. I avoid work at all cost.

Are you thinking of ThirdBreak.org? I attended many of the meetings and got somewhat involved in the effort. However, there were too many personality clashes for it to have been successful, so I drifted away. Looks like the domain, mailing list, and web site are now gone.

Ooops.... ThirdBreak.org is gone, but the hosting server is still alive. Here's the archives of the mailing list:

which apparently died in May 2007.

The name Eric Kellogg sounds familiar, but I couldn't find anything in my correspondence (using Google Desktop Search) with his name.

I see... Yeah, I was just wondering, seeming how you're in the same area and seem to have a wireless lust (I guess one could say). Thanks for the search though.