[Leaplist] an ipcop question

[John Simpson]

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On 2008-12-13, at 0900, Bryan J Smith wrote:
> 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."

fair enough.


> 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).

i understand that- you may also want to clarify that "bridging" here  
refers to the IP layer, or at the very least, passing layer-3  
broadcast traffic (i.e. IP packets where the destination address is  
255.255.255.255) between the wireless and LAN segments. this is  
necessary for DHCP if the client and server are on different sides of  
the LAN/wireless gap.


>> 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.

no problem, you've certainly kept me honest over the years.


> 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.

i fully agree. but when you're standing in compusa, and contemplating  
$70 for a real access point, compared to $30 for a cheap wireless  
ritter, that can be a hard choice to make. at least if people have the  
details about what the different units are capable of, they can make  
an INFORMED decision.

for the record, i've actually seen notes on the retail packaging for a  
few d-link ritters which explicitly say that the unit can be used as  
an access point. this may be true, and i suspect it probably is true,  
for most of the other ritters on the market, but d-link is the only  
manufacturer i've seen so far who actually puts it on their retail  
boxes.

if you're not sure, spend a few minutes reading the boxes, and if the  
store has computers for product research (compusa has a few machines  
with browsers which default to their own web site, for example) do a  
google search for the model numbers and see what kinds of results  
other people have had. otherwise, write down the specific model  
numbers (and versions- linksys has five different "WRT54G" units on  
the market) and do the research at home, then come back the next day  
and buy the one you want.

- --------------------------------------------------------
| John M. Simpson  --  KG4ZOW  --  Programmer At Large |
| http://www.jms1.net/                 <jms1 at jms1.net> |
- --------------------------------------------------------
|   Hope for America  --  http://www.ronpaul2008.com/  |
- --------------------------------------------------------





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