RE: [MLUG] Cable Router

["Spurling, Shannon" <EMAIL:PROTECTED>]

Well, the thing is supposed to be a router, right? Router implies layer
3. MAC addresses are from layer 2. Layer 2 information should not be
carried across a router. If it's bridging Ethernet, then it's not really
acting like a router, and it should not be able to do NAT. 
Thing is, every one is quick to discount the network layer model, but it
works. If manufactures don't stick to the model, their device is bound
to fail. If it doesn't fail, it's going to be buggy, and will be hard to
maintain. The layers in networking are kind of like objects, you don't
mess with what's inside the layer. You feed it stuff from the layers
above and below it, and let it do it's thing.
Functions were supposed to be like that, but too many programmers
figured out that they could mess with Global variables and use the scope
of the variable to mess with stuff. Now we have objects.
So, in summary. Your cable modem/DSL provider cannot filter on MAC
address, unless they are doing some sort of bridging. Some do, but
AT&T/MediaCom don't from what I have seen. Don't go changing MAC
addresses, they aren't supposed to be messed with. If your supposed to
bridge, bridge. The NAT process on your router could, theoretically,
utilize the MAC address, and reassigning your mac address from your PC
to your cable modems outside interface could really screw things up.
Besides, if they are bridging, they would not be able to make you carry
a specific MAC. They would just filter to make sure that only one MAC
was seen across the bridge. One MAC, one device. That device can be what
ever you want. After all, who do they think they are? Microsoft? They
gonna make you call up to unlock your broadband every time you replace
your NIC? :-)

Shannon Spurling
WAN Engineer -Specialist

MOREnet, Network Services, Core Network
3212 LeMone Industrial Blvd.
Columbia, MO 65201

Main:(573) 884-7200   Fax:(573)884-6673

EMAIL:PROTECTED
EMAIL:PROTECTED


-----Original Message-----
From: Brent Deterding [mailto:EMAIL:PROTECTED]
Sent: Monday, November 12, 2001 5:15 PM
To: EMAIL:PROTECTED
Subject: RE: [MLUG] Cable Router


How's that and what are the caveats? The Linksys NATs, meaning it
re-writes the
MAC address. You can configure what MAC it has though. The ONLY way I
know of to
grab the MAC of a box behind NAT is NetBIOS, which very stupidly gives
it out.
Unless of course you can dump the arp cache from the router, which you
shouldn't
be able to (especially if SNMP is off).

Please do elaborate!

-- Brent

-----Original Message-----
From: EMAIL:PROTECTED
[mailto:EMAIL:PROTECTED]On Behalf Of Dale Beams
Sent: Monday, November 12, 2001 10:33 AM
To: EMAIL:PROTECTED
Subject: Re: [MLUG] Cable Router


actually ... ur mac address can be determined even while using a linksys
router ... e-mail is one way
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