Search for PC connection port by MAC address (Cisco)
Sometimes, we need to know which switch port a PC is connected in order to troubleshoot LAN connection problem. Statistics on the access port, such as input error, CRC error, Duplex and speed setting is often very useful for troubleshooting.
In a LAN environment with hundreds of PC and poor documentation, it is difficult to locate which access port a computer is connecting to. Besides following the label on structure cable system, we can use MAC address and few Cisco command to do the job.
In a LAN environment with hundreds of PC and poor documentation, it is difficult to locate which access port a computer is connecting to. Besides following the label on structure cable system, we can use MAC address and few Cisco command to do the job.
- Open Command Prompt.
- Find the MAC address of the PC first:
C:\>ping MyPC
Reply from 192.168.1.4: bytes=32 time<1ms TTL=128
Reply from 192.168.1.4: bytes=32 time<1ms TTL=128
Ping statistics for 10.68.11.49:
Packets: Sent = 2, Received = 2, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms - At this point, the MAC address will be saved in ARP cache in the computer. Use the below command to reveal the MAC address.
C:\>arp -a | findstr "192.168.1.4"
192.168.1.4 00-aa-bb-cc-dd-ee dynamic - (For Cisco IOS command)
The below will show how to find MAC address in IOS. Login to your network Cisco switch to find the connection port: C:\>telnet your_switch
User Access Verification
Password:
your_switch>en
SW2#show mac address-table dynamic address 00aa.bbcc.ddee
Mac Address Table
-------------------------------------------
Vlan Mac Address Type Ports
---- ----------- -------- -----
3 00aa.bbcc.ddee DYNAMIC Gi0/2
Total Mac Addresses for this criterion: 1
(For CatOS)your_switch is an old Cisco switch using CatOS. The below will show how to find MAC address in CatOS. Login to your network Cisco switch to find the connection port:
C:\>telnet your_switch
Cisco Systems Console
Welcome to your_switch
Enter password:
your_switch> en
Enter password:
your_switch> (enable) show cam 00-aa-bb-cc-dd-ee
* = Static Entry. + = Permanent Entry. # = System Entry. R = Router Entry.
X = Port Security Entry $ = Dot1x Security Entry
VLAN Dest MAC/Route Des [CoS] Destination Ports or VCs / [Protocol Type]
---- ------------------ ----- -------------------------------------------
3 00-aa-bb-cc-dd-ee 3/8 [ALL]
Total Matching CAM Entries Displayed =1 - (IOS)
We know that myPC is connected to your_switch via port Gi0/2. Let's check if Gi0/2 is connected to another Cisco switch, not directly to myPC. Cisco Discovery Protocol(CDP) must be enabled in order to use the below command.
your_switch#show cdp neighbors Gi0/2
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID Local Intrfce Holdtme Capability Platform Port ID
core_switch Gig 0/2 142 R S I WS-C4507R Gig 1/1
(CatOS)We know that myPC is connected to your_switch via port 3/8. Let's check if 3/8 is connected to another Cisco switch, not directly to myPC. Cisco Discovery Protocol(CDP) must be enabled in order to use the below command.
your_switch> (enable) show cdp neighbors 3/8
* - indicates vlan mismatch.
# - indicates duplex mismatch.
Port Device-ID Port-ID Platform
----- -------------- -------------------- ---------
3/8 your_switch2 GigabitEthernet0/1 cisco WS-C3560-24TS - (IOS) At this point we know that myPC is connected to your_switch via your_switch2. Let's go to your_switch2 and find out which access port myPC is connecting. Please note your_switch2 is using IOS. The below sample is using IOS command.C:\>telnet your_switch2
User Access VerificationPassword:your_switch2>enPassword:your_switch2#show mac-address-table address 00-aa-bb-cc-dd-eeMac Address Table-------------------------------------------Vlan Mac Address Type Ports---- ----------- -------- -----3 00aa.bbcc.ddee DYNAMIC Fa0/13
Total Mac Addresses for this criterion: 1 - We then know that myPC is connected at FastEthernet port 13.
- (IOS)To know more information about that access port, use the below command:your_switch2#show interfaces Fa0/13FastEthernet0/13 is up, line protocol is up (connected)Hardware is Fast Ethernet, address is 0018.7300.1122 (bia 0018.7300.1122 )MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,reliability 255/255, txload 1/255, rxload 1/255Encapsulation ARPA, loopback not setKeepalive set (10 sec)Full-duplex, 100Mb/s, media type is 10/100BaseTXinput flow-control is off, output flow-control is unsupportedARP type: ARPA, ARP Timeout 04:00:00Last input never, output 00:00:01, output hang neverLast clearing of "show interface" counters neverInput queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0Queueing strategy: fifoOutput queue: 0/40 (size/max)5 minute input rate 50000 bits/sec, 11 packets/sec5 minute output rate 125000 bits/sec, 19 packets/sec17009916 packets input, 2224460537 bytes, 0 no bufferReceived 49139 broadcasts (0 multicast)0 runts, 0 giants, 0 throttles1 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored0 watchdog, 28 multicast, 0 pause input0 input packets with dribble condition detected53834839 packets output, 3153486266 bytes, 0 underruns0 output errors, 8 collisions, 2 interface resets0 babbles, 35 late collision, 0 deferred0 lost carrier, 0 no carrier, 0 PAUSE output0 output buffer failures, 0 output buffers swapped out
- (IOS) Can search via ARP cacheyour_switch2#show ip arp vrf yourvrfname vlan_number | include yourMACaddress
Comments
your post's to be just what I'm looking for. Does one offer guest writers to write content for yourself? I wouldn't mind writing a post or elaborating on a lot of the subjects you write in relation to here. Again, awesome website!
my web site >