Spoofing MAC addresses

[timco]

Hi

I want to set up a small network at home (three PCs and one Mac) so that they can share a broadband cable modem connection. I am going to buy a router - Linksys BEFSR41, a bunch of Cat 5 cables and a NCI card for each PC (Mac has built-in Ethernet).

So far as I can find out, I need to plug the router into the cable modem (the "WAN" port) and then plug each PC's Ethernet card into the router, set up the router to use DHCP and hey presto! (By the way, connection sharing isn't "officially" supported by the ISP).


My ISP is one of those that registers MAC addresses, so I need to "spoof" this, which the router allows me to do. So, when the cable guy comes and installs the cable modem and plugs it into one of the PCs, that PC's ethernet card's MAC address will be the one that's registered. I then set up the router to spoof this address using its built-in software.

Each network card has a unique MAC address. So does this mean that I can't then use the spoofed card on the network (as there would be two MAC addresses the same) as the Linksys manual that I downloaded suggests? So I'll have to buy one more Ethernet card than I actually need and use the spoofed card as a paperweight or something?

Any help would be appreciated.

 

[JackMDS]

I have the same arrangment with SMC Barricade.

The original MAC is in one of the network computers, and the Barricade is cloned with same MAC.

I have no problems, my guess is that the LinkSys will do the same.

 

[ScottMac]

The MAC presented to the ISP side of the link will be the MAC of the router. If you just use that address when the installer shows up.Tell him you're only using the LinkSys as a firewall...the ISPs all recommend some kind of firewall, so they shouldn't object.

Most of the installer know the user is gonna network when they're gone...as long as you don't junk up their system, I don't think they'd care.

Routers only forward the IP address (or other layer three address). The MAC address associated with the source IP address is always the last router transitioned, or the originating host.

FWIW

Scott