Security- two computers - shows three addresses

  Bmay 16:03 17 Apr 06
Locked

Please bear with this longwinded explanation but I am a silver surfer and a novice at this networking.
I have a US Robotics router connected to my desktop pc and my NTL modem. I have a wireless enabled laptop laptop that connects to the router and have set up a network between the two computers. Both access the internet independently. For security I have set the router only to allow the addresses of the two computers to access the internet as well as a network key.
When I look at the host name page there is a third address using my desktop pc's name and with an address of numbers 52-41-53-20-00-02.
It loads within 30 seconds of the desktop every time I switch on this machine.
Please can anyone what this set of numbers might be.
p.s.I disconnected all my peripherals in case it was one of them but the same thing happened.

  mgmcc 16:31 17 Apr 06

I'm not sure exactly what "host name page" you are viewing but, assuming it is in the router's settings, it might be the MAC address of either the router itself or of the Cable Modem.

It is also possible that, if you have at some point accessed the router with a 'wired' ethernet connection, it has retained details of this as well as the wireless connection.

If you go to "Start > Run", type CMD and click OK, this will open a Command Prompt window. At the prompt, type...

IPCONFIG /ALL

...and press Enter. This will display details of all adapters in the PC. The "physical address" is the adapter's MAC (Media Access Control) address. You can see if one matches the number you have quoted.

  Bmay 17:49 17 Apr 06

Sorry my explanation was not clearer....I am in the basic settings page of my router and am on the page for LAN&DHCP server. At the bottom is a list with four columns.... Host name - Ip Address - MAC Address - Lease Expires.Of the three addresses I see under Host name two are the mac addresses for my desktop and laptop. It is the one consisting of pairs of numbers I don't understand.
I did the ipconfig thing and it only lists the mac address for the desktop. Is there a simple way I could find out the mac address of the router or modem?
Everything works fine but it took a lot of trial and error to get this far so I don't want to upset the system but I worry about security.

  Aargh 18:13 17 Apr 06

If you know the mac addresses for your computers, the third address is likely to be your router. On my Belkin there is a sticker on the bottom with the WLAN & WAN/LAN mac addresses - is there a sticker on yours?

If your router software utility allows DHCP Client rules or mac address filtering, try setting your router up to block access by the suspect mac address. You will soon find out if it is your router - you will lose conection!

  Bmay 17:49 18 Apr 06

Why didn't I think of looking underneath!! I found that both modem and router had mac addresses on sticky labels. Alas neither were the troublesome string of numbers.
However tried new ploy ....there is an option to specify Start IP and End IP and as my desktop and laptop Ip addresses ended with 100 and 101 and the unknown numbers ended with 102 I changed start to 100 and end to 101 (it had been 199.
Now when I check the DHCP Server table only my machines are shown ....and fingers crossed everything else is working as it should. Thanks for your suggestions as now I know a bit more than I did before.

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