cancel
Showing results for 
Search instead for 
Did you mean: 

[Resolved] Is this mac address, 00:ef:a3:12:3....... generated by Plusnet?

inkyfingers
Newbie
Posts: 9
Registered: 16-02-2011

[Resolved] Is this mac address, 00:ef:a3:12:3....... generated by Plusnet?

I have a Linux PDA, which is a Skytone Alpha 400 - a toy - modified to boot Debian Lenny off more than 1 SD card. I now find I have two devices with one mac address:  00:ef:a3:c1:00:03.
Can this address be positively identified as provided by Plusnet and/or my router Thompson TG585 v7?
The default  Skytone Alpha 400 still runs with its “hard mac addresses” - I have positively identified the first part of the address with the device manufacturer.
8 REPLIES
Community Veteran
Posts: 1,101
Registered: 10-09-2010

Re: Is this mac address, 00:ef:a3:c1:00:03 generated by Plusnet?

The only way you should have two devices with the same MAC is if you configured one or both manually or used a feature called MAC cloning (something to be avoided unless you positively, absolutely know you need it).
You will need to change one of them to something else.
Your router doesn't care what MAC addresses are used so long as they unique, and if they are behind your router Plusnet never even get to see the MAC addresses as all traffic Plusnet see has the WAN interface MAC address of your router.
As to who generated that MAC address it's difficult to say, but I think perhaps some software, because the address is not within anyone's allocated range.
http://www.macvendorlookup.com/
Community Veteran
Posts: 6,366
Thanks: 490
Fixes: 45
Registered: 30-07-2007

Re: Is this mac address, 00:ef:a3:c1:00:03 generated by Plusnet?

Quote
have a Linux PDA, which is a Skytone Alpha 400 - a toy - modified to boot Debian Lenny off more than 1 SD card. I now find I have two devices with one mac address:  00:ef:a3:c1:00:03.

I take it that what you are saying is that you can boot the PDA with two different operating systems. I suspect the 'system name' when Debian is booted is different from the one when the default OS is booted. The network card will use the same MAC and therefore at sometime the router will have 'seen' two, apparently different, systems with the same MAC and remembered them. SInce both can't possibly be in use at the same time then its not a problem.
inkyfingers
Newbie
Posts: 9
Registered: 16-02-2011

Re: Is this mac address, 00:ef:a3:c1:00:03 generated by Plusnet?

Quote
but I think perhaps some software, because the address is not within anyone's allocated range.

I guess it is down to my bootstrapping technique then!
Quote
I take it that what you are saying is that you can boot the PDA with two different operating systems

Three - default, and (actually more than) 2 SD cards. I am trying to get at least one error-free!
Quote
SInce both can't possibly be in use at the same time then its not a problem.

I have a problem (although my two devices which I know are using hard mac work fine) I have had a run of these errors when swapping between different cards
Auto eth0 is erratic - network is unreachable - but will usually connect at third attempt by Auto eth0, but never by dhclient.
Also noted error message at shutdown: DHCPRELEASE on eth0 ... network is unreachable.
I see that I need to change the mac - I cannot document this, but it seemed I "lost" a new MAC that I tried, and wondered if it had been replaced by the router - hence my original question.
Thanks for the help  Smiley
Community Veteran
Posts: 6,366
Thanks: 490
Fixes: 45
Registered: 30-07-2007

Re: Is this mac address, 00:ef:a3:c1:00:03 generated by Plusnet?

I suspect that the DHCP server on the router might be getting confused. If you swap between different cards faster than the router DHCP lease time ( quite likely ) then the DHCP server may have an active lease for the same MAC BUT a different system name. Goodness knows what it will do under these circumstances ?
inkyfingers
Newbie
Posts: 9
Registered: 16-02-2011

Re: Is this mac address, 00:ef:a3:c1:00:03 generated by Plusnet?

Quote
If you swap between different cards faster than the router DHCP lease time

I hadn't considered that - I don't know what sort of length lease time are ...
but it features in my error messages!

It also fits with my workaround which is - using my pc pointing to Gateway 192.168.1.254 - always to delete any SD card device, when finished a session, then a cold-boot of any device will connect perfectly and show in Gateway as "unknown-...correct-mac-address".
An other issue is that the SD card devices do not have java-enabled-browser, are not therefore configurable on the web interface, and I have not fully read my manual on configuring by hand. That looks like my next task!  Smiley Thanks

Community Veteran
Posts: 1,101
Registered: 10-09-2010

Re: Is this mac address, 00:ef:a3:c1:00:03 generated by Plusnet?

Quote from: MisterW
I suspect that the DHCP server on the router might be getting confused. If you swap between different cards faster than the router DHCP lease time ( quite likely ) then the DHCP server may have an active lease for the same MAC BUT a different system name. Goodness knows what it will do under these circumstances ?
I don't think that will be a problem*, but many DHCP servers allow you to pin IP addresses to MAC's so it should just give the same IP always.
*the more I think about it, the more I just can't see an issue with it at all.
Community Veteran
Posts: 6,366
Thanks: 490
Fixes: 45
Registered: 30-07-2007

Re: Is this mac address, 00:ef:a3:c1:00:03 generated by Plusnet?

Quote
I don't think that will be a problem

I agree, it shouldn't be a problem, the DHCP server will see the same MAC and SHOULD just issue the same IP. However some routers hold a list of connected clients, often using the system name. In this case I'm just not sure what the router ( and we know the TG585 is not the best one in town! ) will do.
inkyfingers
Newbie
Posts: 9
Registered: 16-02-2011

Re: [Resolved] Is this mac address, 00:ef:a3:12:3....... generated by Plusnet?

There is something non-standard about the mac address that I have yet to discover!
I have to accept for the moment that I cannot change it by hand or macchanger.
Thanks for the help and the pointers