Simon, True "bridges" must know which side of the "bridge" a particular mac address resides on. If they are to forward at the hardware level, this is a simple table inside the bridge which keeps the hexadecimal mac address of of the "my" side and the "other" side, drops incomming wire packets destined to those machines on "my" side (because they don't need forwarding) and responds by proxy for those packets which need to get to a mac on the "other" side of the bridge and forwards them to the corresponding bridge device on the "other" side. (oversimplified - they also handle broadcasts, etc)
Now these tables of mac addresses can be small if it's inside your house (5? 8 computers?) - mid size (100 computers?) for small companies, or big (4096?) for those large corporations with something bigger than a /24 and large offices with all sorts of internal routing tables. What Cisco is doing is making the "big" guys pay up - if they are linking two buildings with an AP and a WGB (workgroup bridge) - they are allowed to link 8 devices before the table is full. Consult their spec sheets to see how many mac addresses other devices can handle in bridge mode before they are "full". One orinoco device I had to deal with held 1 address only - it was intended to connect a printer or one computer to a wireless net and no more. A trick to get around this is use their cheaper "home" (8 mac) hardware and stick a router on it, then ROUTE instead of BRIDGE the packets. My mountaintop is linked almost 8 miles using just standard (i.e. cheap) cisco APs and WGBs - but I run 256 IPs up to the router on the mountain using just one MAC (the router's MAC) - it then sends the packets to the proper AP for the sector where the client is located. The cisco hardware just sees two MACs talking to each other an awful lot (they're both routers!) That's the long and the short of why building to building bridges cost so much - they know a corporate customer is buying it, and will gladly fork over the needed cash. The marginal cost to add the larger MAC table as you and I both know is virtually nothing with the prices of memory today. It's like OCTEL selling an 80 meg (MEG!) disk drive for $4500 with a copyright message in the boot sector and claiming it is "storage software" to prevent others from selling 80 MB disk drives to go into an Octel system. Companies just want more $ for bigger systems - and the more money for the least hardware costs make for better returns on investment. Everett > Is there any good reason why the Cisco Aironet bridges cost so much > more than the APs? Looking at something like the D-Link AP900+ which > can operate in AP or bridge mode, and reading some other comments, it > seems like they're just taking advantage of ignorant corporate > customers. > > I need to set up a long-distance link (like 25 km) and I want to put in > more reliable radios for that section of the network, but I don't want > to pay the cisco "bridge tax". > > simon > > -- > www.simonwoodside.com :: www.openict.net :: www.semacode.org > 99% Devil, 1% Angel > > -- > general wireless list, a bawug thing <http://www.bawug.org/> > [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless > -- general wireless list, a bawug thing <http://www.bawug.org/> [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless
