Solved

Hoe to find ip address of neighbouring switch

Posted on 2009-05-11
5
883 Views
Last Modified: 2012-06-27
I have a Cisco 1841 series router that it connected to a 3com switch through the FastEthernet port. I am trying to find out the ip address of the switch attached to the router.

I have tried a SH CDP NEI but when I do this it informs me that the router is connected through the interfaces f0/0 and f0/1.

Is there any other command that I can loo at without trying to telnet to all the devices in the arp table?
0
Comment
Question by:MartynLawson
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
5 Comments
 
LVL 9

Expert Comment

by:jfrady
ID: 24353708
No.  CDP is a proprietary Cisco protocol.  The ways you can find the IP:

Log into the console
Look in the ARP cache on the router and associate with the MAC address on the label of the switch
Use a freeware app to do a ping scan of your network range
Try the default IP of the switch

Looking through aRP caches etc. won't do you much good if the switch is on a different subnet than your network for some reason.  Easiest bet is to go in to the console port.
0
 
LVL 1

Accepted Solution

by:
Teacish earned 250 total points
ID: 24353840
Also if your computer is connected to the switch then you can type arp -a from the command prompt and compare the mac addresses in the list with the sticker on the bottom of the switch as ifrady said.
0
 
LVL 1

Expert Comment

by:Teacish
ID: 24354067
Although thinking about it if its managed then each port is going to have a mac address.. It would have to be done by a network scanner really.

Try using Angry IP Scanner and scan your network range and see if you can find it on there.
0
 
LVL 9

Assisted Solution

by:jfrady
jfrady earned 250 total points
ID: 24354163
Teacish - If it is a Layer 2 switch there will only be one MAC address that is associated with the management interface.  The only time a switch will have multiple MAC addresses is if it has multiple Layer 3 networks.  

Using ARP -a will only show the address if it is on the same subnet and your machine has tried to contact it.  Sometimes you can do a ping to x.x.x.255 and then do ARP -a to see devices on your network.  This is not a valid way however as most devices would take that as a smurf attack and not respond.  And in this case we do not know if the switch management interface is even on the same subnet or configured from default.

The easiest way in your case Martyn is to plug in to the console or use one of the other methods mentioned.
0
 
LVL 1

Author Closing Comment

by:MartynLawson
ID: 31580107
Thanks Guys :)
0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
SCCM, SCOM or Something Else 6 60
Auto Qos question 1 23
SSL-VPN 1 48
IP Jumping 6 18
In the hope of saving someone else's sanity... About a year ago we bought a Cisco 1921 router with two ADSL/VDSL EHWIC cards to load balance local network traffic over the two broadband lines we have, but we couldn't get the routing to work consi…
This article will inform Clients about common and important expectations from the freelancers (Experts) who are looking at your Gig.
Viewers will learn how to connect to a wireless network using the network security key. They will also learn how to access the IP address and DNS server for connections that must be done manually. After setting up a router, find the network security…
Get a first impression of how PRTG looks and learn how it works.   This video is a short introduction to PRTG, as an initial overview or as a quick start for new PRTG users.

749 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question