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Cisco IOS show DHCP host names

Posted on 2007-04-02
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What is the cisco IOS command to sho all DHCP clients and host-names. I know sh ip dhcp binding shows the MAC addresses but I need to also find the host names which relate to the IPs. Thanks.
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Question by:jsm11482
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by:batry_boy
ID: 18841106
There is not a command in the Cisco IOS that will show you the hostname of a DHCP client...it simply does not keep this information.

If you want to find out the hostnames associated with the IP addresses or MAC addresses, then I would recommend a utility called Angry IP Scanner...quick, simple, free, and doesn't require an installation!  Check it out here:

http://www.angryziber.com/ipscan
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by:jsm11482
ID: 18841117
Thanks. I'll give it a try tomorrow.
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by:batry_boy
ID: 18841126
You give it a range of IP addresses to scan and it can show you the DNS hostname, the NetBIOS name, the MAC address, the name of the user account currently logged in, and can even scan for open ports, plus it's fast...use it quite often myself.
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by:jsm11482
ID: 21203815
It's been a while but I did try this. The problem is that the hosts are behind firewalls so how can I figure this out? I have access to the router. Is there any command I can run?
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by:batry_boy
ID: 21204152
You say the hosts are behind a firewall but you have access to the router, so I'm a little confused on the network topology here.  Can you submit a simple network diagram showing the placement of the hosts in relation to the firewall and/or router you mention as well as where you are trying to see the hostnames from, i.e. your PC?  That will provide a clearer picture of how to do what you are wanting to do, if it's possible at all.
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by:jsm11482
ID: 21204342
Basically someone is hoggin the network and I know their IP but I can not resolve the IP to a hostname - it appears they are behind a firewall. We basically have the main router which is the DHCP server. All clients/hosts get their IP from the router either via the wired or wireless network. I can either run a command on the router to figure out who the culprit is or I can run some softare on my laptop. I hope that makes sense, thanks!
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by:batry_boy
ID: 21204575
Is the IP on the same subnet as where you are checking from?
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by:jsm11482
ID: 21204631
Yes. And I have the MAC addreses, which I got by running: sh ip dhcp binding. If that helps.
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by:batry_boy
ID: 21205558
Then if it is a Windows machine, it should respond to Netbios requests.  If it is, you can use the "nbtstat" command from a Windows command prompt and specify the IP address and it should return the hostname and possibly the user ID currently logged into that host.  You have to be on the same subnet as the target IP when using this command because Netbios is broadcast-based traffic.

So, for example, if the target IP is 10.1.1.5, then you could try issuing the following command:

nbtstat -A 10.1.1.5
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by:jsm11482
ID: 21205615
Thank you, I did try this and all it returns is Host Not Found. This leads me to believe either NetBios is disabled or blockded (?) or it is one of the Macs here. So, let's pretend I need to know the hostname of the machine and it could me a mac or a pc. Thanks!
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by:batry_boy
ID: 21205652
Do you use managed switches where you could look at the MAC address table to find out which switch port that MAC address is connected to and then physically track down the wall jack that it goes to?  I think I would try that next.
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by:jsm11482
ID: 21205671
No we don't have managed switches here - I did think of that though - I have two people in mind who could be the culprit and I could find out their jack number but I can't relate it to the MAC anyway. Also, they are almost certainly using wireless.....good idea though......anthing else? ;-)
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batry_boy earned 125 total points
ID: 21208630
If you suspect that these hosts are behind firewalls, then I don't think you're going to be able to determine the hostnames remotely.  It sounds like these individuals are possibly operating outside the sanctioned parameters of company policy.  I think I would try to ferret out the individuals by blocking all IP traffic from those IP addresses with an ACL on the router and see if they speak up about the lack of connectivity.

If that sounds too much like being a "network nazi", then you may have to do this the old fashioned way and just ask the individual to show you their MAC address for identification purposes or whatever you want to tell them.

Maybe some other expert out there has some better suggestion, but I think I would take the more "hands on" approach at this point!  ;)
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