how to find ip --switching

Answered Question
Dec 19th, 2009

Hi seniors,

I am new in networking field and studying Cisco stuff on daily basis. Questions are -

1- How to know the port of the device if IP is know but MAC is unknow ?

2- Say there are 8 switches attached in a stack, and one PC is attached to a switch , only IP is know, how to know what is that particular switch the PC is attached to ?

Thanks you all.

Tahir.

I have this problem too.
0 votes
Correct Answer by Jon Marshall about 6 years 11 months ago

tahir1234 wrote:

Hi seniors,

I am new in networking field and studying Cisco stuff on daily basis. Questions are -

1- How to know the port of the device if IP is know but MAC is unknow ?

2- Say there are 8 switches attached in a stack, and one PC is attached to a switch , only IP is know, how to know what is that particular switch the PC is attached to ?

Thanks you all.

Tahir.

Tahir

If you only know the IP then you need to go to the L3 device ie. router or L3 switch that is the default-gateway for the client. Then

1) "sh arp | include "   will give you the mac-address

then log onto one of the switches and

2) "sh cam "

the result will either be the port the device is attached to or it may be a trunk port. If it is a trunk port then you will need to find out the switch on the other end of the trunk link, log onto that switch and then repeat step 2.

You can use CDP to find details of device attached via trunk ie.

sh cdp neigh detail

Jon

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Loading.
Correct Answer
Jon Marshall Sat, 12/19/2009 - 09:36

tahir1234 wrote:

Hi seniors,

I am new in networking field and studying Cisco stuff on daily basis. Questions are -

1- How to know the port of the device if IP is know but MAC is unknow ?

2- Say there are 8 switches attached in a stack, and one PC is attached to a switch , only IP is know, how to know what is that particular switch the PC is attached to ?

Thanks you all.

Tahir.

Tahir

If you only know the IP then you need to go to the L3 device ie. router or L3 switch that is the default-gateway for the client. Then

1) "sh arp | include "   will give you the mac-address

then log onto one of the switches and

2) "sh cam "

the result will either be the port the device is attached to or it may be a trunk port. If it is a trunk port then you will need to find out the switch on the other end of the trunk link, log onto that switch and then repeat step 2.

You can use CDP to find details of device attached via trunk ie.

sh cdp neigh detail

Jon

tahir1234 Sat, 12/19/2009 - 10:28

Jon thanks for reply.

One think I forgot to ask in previous post,

-for the same scenarious  , what would if switches are CATOS running on them,,

Thanks again.

Ganesh Hariharan Sat, 12/19/2009 - 10:27

Hi,

login into switch then issue a command show arp after wards with mac you can issue show mac-address | in specific mac .

Hope that helps

Regards

Ganesh.H

Reza Sharifi Sat, 12/19/2009 - 11:11

Hello Tahir,

For Cat OS you use

sh cam

For native IOS you use

sh mac-address-table

HTH

Reza

Actions

This Discussion