MAC Addresses
Author
Discussion

bobthemonkey

Original Poster:

4,211 posts

247 months

Tuesday 7th November 2006
quotequote all
Right - not too good on this networking business

Is there a way to connect two computers to a network, but only have ONE MAC address?

I only have access to one ethernet socket, which is linked to one MAC address. I can change the address its linked to, but it can only handle one MAC address at a time.

I'm thinking a wired router and a couple of lengths of Cat5 may be the answer, but would like confirmation first.

slinky

15,704 posts

280 months

Tuesday 7th November 2006
quotequote all
a MAC address is an address that is hard coded into the hardware.. I don't think you'll be able to "spoof" it easily

Wired router with NAT may do the job, but if there is MAC address filtering, you may struggle to get around it.. (let me guess, you're using a cable internet connection??)

slinky
587racing.com

zumbruk

7,848 posts

291 months

Tuesday 7th November 2006
quotequote all
Some NICs allow you to modify the MAC, so this is possible, but it's almost always a mistake. What's the *real* problem that the OP is trying to solve? Is it an ISP that only allows one machine to be connected to the network, a cable ISP, perhaps?

In which case, just connect a router to the ISP, which will only see the MAC of the router (MACs are local a LAN) and connect all your PCs to the router.

bobthemonkey

Original Poster:

4,211 posts

247 months

Tuesday 7th November 2006
quotequote all
It's a uni network

zumbruk said:

In which case, just connect a router to the ISP, which will only see the MAC of the router (MACs are local a LAN) and connect all your PCs to the router.


Thats what I was thinking of doing, but would it work in this case as its connecting to a local netwrok, rahter than straight to the net. net access is via a proxy server btw.

Edited by bobthemonkey on Tuesday 7th November 21:11

UpTheIron

4,058 posts

299 months

Tuesday 7th November 2006
quotequote all
bobthemonkey said:
I'm thinking a wired router and a couple of lengths of Cat5 may be the answer, but would like confirmation first.
That should work, assuming that the 'security' solution used to prevent more than one PC being connected is as simple as you describe.

Another option would/could be to set up internet connection sharing on the PC you use to connect to the network, and then connect the other PC via the first one.

mattley

3,039 posts

253 months

Tuesday 7th November 2006
quotequote all
I recon it depends on their reason for implementing this rule.

If it's for useage accounting and basic security then yes, a router should do the trick.

If it's for full on traffic monitoring then a router won't work as the they'll be checking at a packet or datagram level and IIRC the originitaing and destination MACs are carried in the L2 headers so they'll know that it's destined for a machine that isn't your router.

I'd just ask the uni network admins, half the time on uni networks, it's some stupid from above policy that pisses them off as well so they'll be more than happy to tell you the best answer.

Mr Beckerman

5,346 posts

258 months

Tuesday 7th November 2006
quotequote all
Which Uni............. sonar

bobthemonkey

Original Poster:

4,211 posts

247 months

Tuesday 7th November 2006
quotequote all
why do you ask?

ThePassenger

6,962 posts

266 months

Wednesday 8th November 2006
quotequote all
So, basically you have one CAT5 jack on a network.
This port is coded so that only the correct MAC address can pull an IP.
You want to run multiple computers over this network, however you are unable to or unwilling to be perpetually swapping over the registered NIC.

Right. I can, off the top of my head think of two cheap n' cheerful ways of getting around this.

1. But a WiFi AP/Router. Register it's MAC. Tell it to begin NAT/MASQ and DHCP. Fit all of your other machines with WiFi card.

2. Grab a a 486... something old, crappy and can run without a fan (Strap a Socket A cooler to the beast). Fit a dinky little HDD on it and two NIC's (one being the registered unit). Then install Linux via some method which doesn't have it trying to boot a GUI.
Install DHCPCD, DNSMASQ and IPTABLES.
Jot down which network card is which on the system, then configure DHCPCD to pull an IP from the registered NIC. DNSMASQ to handle IP/DNS servives for the other machines, IPTABLES to act as NAT (rusties 3 line MASQ config will do the job).

Mr Beckerman

5,346 posts

258 months

Wednesday 8th November 2006
quotequote all
bobthemonkey said:
why do you ask?


Just interested......

aldi

9,292 posts

268 months

Wednesday 8th November 2006
quotequote all
Re. level 2 headers mentioned earlier, I didn't think NAT worked through encapsulation, I thought the NAT device just keeps a table of mappings? That being the case I think it would fool the average switch's port level security.

Edit: If it doesn't, they make good money on ebay second hand

Edited by aldi on Wednesday 8th November 09:18

Leithen

14,097 posts

298 months

Wednesday 8th November 2006
quotequote all
Mr Beckerman said:
bobthemonkey said:
why do you ask?


Just interested......


University A seems to be far enough away from University B


laugh laugh

bobthemonkey

Original Poster:

4,211 posts

247 months

Wednesday 8th November 2006
quotequote all
brighton, bit rought up there

Mr Beckerman

5,346 posts

258 months

Wednesday 8th November 2006
quotequote all
We like to keep one step ahead of the little darlings on the residential network.

zumbruk

7,848 posts

291 months

Wednesday 8th November 2006
quotequote all
aldi said:
Re. level 2 headers mentioned earlier, I didn't think NAT worked through encapsulation, I thought the NAT device just keeps a table of mappings? That being the case I think it would fool the average switch's port level security.


MAC addresses never make it off the local LAN. And no, NAT doesn't work by encapsulation, it rewrites the packet headers, and it has nothing to do with MAC addresses anyway.

onomatopoeia

3,526 posts

248 months

Wednesday 8th November 2006
quotequote all
ThePassenger said:

2. Grab a a 486... something old, crappy and can run without a fan (Strap a Socket A cooler to the beast). Fit a dinky little HDD on it and two NIC's (one being the registered unit). Then install Linux via some method which doesn't have it trying to boot a GUI.
Install DHCPCD, DNSMASQ and IPTABLES.
Jot down which network card is which on the system, then configure DHCPCD to pull an IP from the registered NIC. DNSMASQ to handle IP/DNS servives for the other machines, IPTABLES to act as NAT (rusties 3 line MASQ config will do the job).



yes Do this.

twin40s

154 posts

286 months

Wednesday 8th November 2006
quotequote all
The Netgear router (RP116 i think) can spoof the mac address of one of the connected PCs.

Dunno if they still sell the exact model any more though