How to find a PC via which port on switch?

Hey gurus

Okay my situation is this. I am labeling our patch panel with the exact names
of PCs that come out of the patch to the switch. But some are not labeled so I am using

show ip arp | i (ip address)

show mac-address-table vlan (#) | i (mac)

but I am not near being a CCNP but am almost a CCNA so I understand quite a bit.

I look into the 3560 and 2950 switches and I see many macs assigned to Gi0/1
and with the commands above. To no avail, I just see Gi0/1...

When I look, I only see 1 Gi0/1 port and 1 Gi0/2 ports what is going on some show
exact port assignments and many show only Gi0/1 only how can that be?

they are in vlan 101 but all Gi0/1.. can someone explain this? why doesnt it show
exact port the PC (ip and mac)are coming in on? why this I will use the term looslely
virtual port of Gi0/1.

Help guys!

Robert

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Comments

techster79

I don't know if I understand you correctly, but...

Gi0/1 sounds like a gigabit port that is connected to another switch or hub, which would give you multiple MAC addresses instead of a single one which would be a single host connected to a port.

If you have a tone generator and wand you can trace where each patch panel port terminates in the office, it takes some foot work but is not difficult.

mikearama

I think techster's nailed it...

G0/1 and 2 are either etherchannels to another device, or are possibly just regular uplinks to multiple devices.

Nonetheless, you're using the right commands. Took me a couple years to figure out what you're doing.

Mike

Aquabat [banned]

that is prolly a trunk port to another switch, that's why all of those nodes are showing up on the same port. i would be a sh cdp ne de, telnet to that switch/ and look at the arp/forward filter table in there.

Netstudent

Dang man, I'm trying to understand what you are saying but its pretty hard. I don;t know if you are trying to figure out why your uplinks show multiple MACS or if you are wondering why only 2 ports show in the output of show mac-address-table vlan 101.

kafifi13

Show mac address address XXXX.XXXX.XXXX

I do this all the time on 2950's, 3550's, 3750 stacks. The only one that is difference is possibly a 6509 Core switch. I do that and locate the port every time.

kafifi13

I think he just wants to lable what PC is connected to what port on a switch correct? if that's the case do what i listed above and put the PC's mac address. I'm a bit confused too but after reading his question i think that's what he wants. Hope it helps. PM if you ahve questions.

itdaddy

I am confused and it shows. hee hee it is hard to explain but some of you guys got it.

when you do the commands I mentioned, you can find which port a certain PC resides
via mac address displaying on the screen. What I encounterd is yes they are Gig trunk ports
but in this switch i was in 3560 I put the cable in myself that coresponds to the pc it is attached to but when you run the commands it only displays many pc/mac address coming from Gi0/1
many many and some are exact correspondence fa0/x to 0030.3232.24bh perfect match
but some were many macs to a single port Gi0/1. MY problem was

I could see the port fa0/5 that our Antivirus server was plugged into cause when i unplugged it from switch connectivity was lost to AV server. But when i telneted to switch it showed only
Gi0/1 correspondence and I did the commands exactly and it shows vlan 100 from Gi0/1.
will try to get a display to show here so you can see what I am talking about. A picture is better.
so will get one to explain. thank dudes. hard to write something you are confused on myself
thanks for replying guys! I understand trunks and such and vlans how they are sent via trunks
but when i show you the image you will see better. thank techies

Robert

itdaddy

Netstudent

both...once i give you the image and explain it better, you can see what i am saying thanks
for even replying. appreciate it....

itdaddy

somethinglike the below (this does look like a trunk output) but
it is only an example if you guys still dont get it. (my fault only)
i will get my exact outputexample (mock output only)

10 0000.0c07.ac02 static ip,ipx,assigned,other Switch
10 0000.e858.01a2 dynamic ip GigabitEthernet2/4
10 0001.e63f.68a3 dynamic ip GigabitEthernet1/1 10 0002.5519.0106 dynamic ip GigabitEthernet1/1
10 0002.551e.0f0f dynamic ip GigabitEthernet1/1
10 0002.557a.1fb6 dynamic ip GigabitEthernet1/1
10 2445.255a.2rf5 dynamic ip, fa0/9
10 0002.557a.1ff6 dynamic ip GigabitEthernet1/1
10 0002.557a.27ef dynamic ip GigabitEthernet1/1
10 0000.255a.2r55 dynamic ip, fa0/8
10 0002.557a.2b2b dynamic ip GigabitEthernet1/1
10 0002.557a.2da6 dynamic ip GigabitEthernet1/1
10 0002.557a.3886 dynamic ip,other GigabitEthernet1/1
10 2345.0000.2r55 dynamic ip, fa0/4
10 0002.a5fb.5b52 dynamic ip GigabitEthernet1/2
10 0003.4798.e60d dynamic ip GigabitEthernet1/2
10 2345.255a.3345 dynamic ip, fa0/7
10 0004.aca3.9226 dynamic ip,other GigabitEthernet2/4
10 0006.2939.039a dynamic ip GigabitEthernet1/2
10 0006.2957.6ea0 dynamic ip GigabitEthernet1/2

this is what I mean. My display is similar but shows many gig ports
but not a specific port and I know the port that I put our AV server in
is in the port I physically put in. I just want to find it via CLI..but my
display show some exact mappings physical port/cable to logical mac mappings.
Does anyone understand. Some of you guys understood me. But I know
what cable I inserted in what port. I want to be able to find these PCs with the CLI
cause some of my CCNP friends said you could but when I looked, I get the gig port mapping to
my AV mac address.

thanks

mikej412

itdaddy wrote:

I get the gig port mapping to my AV mac address.

If the address is mapped to a trunk port, that means the server is plugged into a port on another switch.

Are you sure you're telneted into the correct switch and are you sure you pulled the correct plug?

Don't forget the CAM and ARP tables are cached -- you either have to clear them or wait for the data to expire. And if there was no network traffic, they may drop out of both tables at some point on their own.

bighornsheep

If it's a windows box, there's a command you can use in command prompt.

nbtstat -A <ip address>
or
nbtstat -a <host name>

it'll give you a table with the MAC address of the remote host (even if it's not in the same subnet), you can then look up that MAC in your switches which should tell you exactly which port that host is plugged into.

itdaddy

mikej412 and Big horn,

thanks yeah i found some ports that corresponded to mac addresses already but
when i saw many Gig ports the same one i kind a figured it was maybe a trunk and itis just
posting where they come from..I need to do more investigation. I am just reading the ip address
that our network engineer (outsourced) posted on the switch. and when i unplug the physical
cable the server looses connectivety...

thanks for all your help dudes!

Robert