[Leaplist] an ipcop question

[Bryan J Smith]

On Fri, 2008-12-12 at 18:17 -0500, John Simpson wrote:
> i own at least one device, an old linksys BEFW11S4 9the 802.11b pre- 
> cursor to the WRT54G series) where this is not true. on this unit, the  
> wireless segment is not bridged in with the LAN ports. unicast traffic  
> between wired and wireless works normally, but layer-2 broadcast  
> traffic (devices discovering each others' MAC addresses) is not passed  
> transparently from wireless to LAN, or vice-versa.

I'll rephrase ...

  "Modern 'Ritters (that do bridging between LAN and WLAN segments)
   and APs work the same on the Blue, as long as they are connected
   to the Blue via the "LAN" interface on the 'Ritter."

You are correct, the key is that bridge (layer-2) between LAN and WLAN
segments.  If they only route (layer-3), then that's a problem.
Bridging between 802.3 (Ethernet LAN) and 802.11 (Wireless LAN), two
very different framing (briding, layer-2) protocols, and requires some
advanced capabilities.  So those cheap, early 'Ritter just did IP
forwarding (layer-3).

Bridging itself is completely different for 802.11 than 802.3, and it is
not "transparent."  I.e., 802.3 uses a destination and source, and could
care less if there is a bridge or not, so any bridging is transparent
between the end-nodes.  802.11 always has destination, source and bridge
(AP) in the frame itself, so bridging is required.  That's some added
detail, although today's MACs in 802.11 WLAN devices are typically ARM9
and more powerful, so they do bridging in their firmware (and faster
than software).

> while bryan is "mostly" correct, you need to be aware that there are a  
> few exceptions out there. if you're buying a new wireless device and  
> plan to use it for an ipcop "blue" segment, go with a real AP if you  
> can, or at least find one which has been verified to work in a  
> "gateway on the LAN segment" configuration, such as my netgear  
> WGR614v9. or get one where you can re-flash the firmware, and the  
> firmware supports "true AP" operation.

And I'm glad you reminded myself (among others) that they do exist.  I
wouldn't want the user to get frustrated when I overlooked that fact.
Thanx for pointing it out.

In any case, I still prefer a "real AP."  They cost more because they
typically include a much more powerful microcontroller on-board to
handle 2-3 dozen nodes associated, instead of just a couple in a home
network.


-- 
Bryan J  Smith                Professional, Technical Annoyance
Mugshot Homepage:  http://mugshot.org/person?who=58wDcGKx6NcZAb
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           Fission Power:  An Inconvenient Solution            


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