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Clients and Ports

Jeff Mock
Occasional Visitor

Clients and Ports

I'm trying to figure out which computers (IP addresses) are plugged in to which ports on my Procurve 2650 Switch. I'd rather not have to trace the physical wires all the way back to the actual computer. Is there anything that could tell me which clients are going into which ports?
3 REPLIES
Ron Kinner
Honored Contributor

Re: Clients and Ports

If you just want to find one PC and you know the IP address you want to find then you just ping it from your pc then (assuming you have Windows) Start,Run, cmd, OK to bring up the black cmd screen and then type:

ping A.B.C.D

(After it finishes, type)

arp -a

look for the IP address in the table and get the Physical Address associated with it. Your friendly router will also have most of the PCs in its arp table which will show you the IP and MAC for every PC that has sent traffic through in in the last 4 hours or so.

sh arp

If it speaks Cisco IOS will show you the router's arp table.

Then log onto your switch and use the command line to type:

show mac-addresses

This will show you what mac addresses are attached to each port. I used to save the text to txt file then import it into an Excel file then sort it by the MAC.

If you have a lot or want to know where every one is then there are free programs you can get that will ping each possible subnet address on your network and report back on every IP/MAC combination they find.

http://insecure.org/nmap/
is one. There are many out there.

Then you can save that info to a txt file and import into Excel and sort by MAC and compare it to the list of MACs from the switch. If you make the list of MACs right after running the scanner, there should be almost a one to one correspondance between the two files.

Ron

Ashly A K
Honored Contributor

Re: Clients and Ports

hi!

Tracing the phycical cable will drive you mad!!! Don't even think of that.
The bets way is to long in to the switch, ping the IP. then get the ARP and MAC Table. Match the both, you will know what is connected where!!

-Ashly
http://www.geocities.com/helponhpopenview
Hugo Tigre
Trusted Contributor

Re: Clients and Ports

hi Jeff,

If you want to find computers that are connected to your network but are not part of your domain, like personnel computers in workgroups, you will need to sniff the traffic to find their mac-address and then work your way through the switches to locate them.

You can also access DHCP to see with computers are using your ip subnet, but this as two problems. one is because the computer can have manually configured ip address. Two is because dhcp doesn't tell you with workgroup it is.

A good packet sniffer is wireshark, and you can download it for free and use it. Just tell the sniffer to sniff you network card and them try to connect to a workgroup that you detected in windows, you probably get a time out or a error from windows because you don't have permission to log in that workgroup. Then stop the sniffer and look for netbios packets, and if you look carefully you will find the mac-address of the computers inside that workgroup.


hope that helps.

best regards,
Hugo