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We use ssh to connect to cisco switches through linux box.it prompts for a password and then we are logged in.I was just wondering if i could find out a way to list out all the cisco switches connected to the linux machine.Approximately there are around 3000 switches that i can ssh to from the linux machine.

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Are you allowed to run nmap or other port scanning software? That would give you a list of devices which are connected to your network which you can then filter by MAC. (Cisco MACs: See miniwebtool.com/mac-address-lookup/?s=cisco ). Or use ZenMap (a GUI frontend) to do the same. – Hennes Apr 11 '13 at 5:04
    
yes i am allowed – munish Apr 11 '13 at 5:10
up vote 1 down vote accepted

You did not specify which Linux distribution. If it is one with a package manager then add the nmap package. If it has no package manager or if you want to compile it yourself go to http://nmap.org and get the tarball.

Compile it and test it on a few known host (a few so initial tests are quick).

Examples:
nmap -v 127.0.0.1 (-v is verbose)

nmap 172.16.0.0/12 (One way to scan a large range)

nmap 192.168.1.1-254 (an other way to specify a range)

In your case you might want the flags s and n.

nmap -sn 192.168.1.252

Starting Nmap 5.51 ( http://nmap.org ) at 2013-04-11 07:22 W. Europe Daylight Time
Nmap scan report for 192.168.1.252
Host is up (0.00s latency).
MAC Address: 00:1E:E5:7A:47:5B (Cisco-Linksys)
Nmap done: 1 IP address (1 host up) scanned in 0.39 seconds

Use these to scan your entire own network amdlog the results to a file. Then sort that on the brand name or MAC and you have your desired list.

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Nmap supports arp-scan which would be effective in a LAN. Since all you need is the MAC, TCP port scan can be omitted. It's important to run nmap as the superuser (sudo works too):

 $ su -c 'nmap -PR -oN arp-scan.txt 10.3.0.0/27'
 Password:

 (...)

 $ grep '^[NM][Am]' arp-scan.txt
 Nmap scan report for tryggve.lan (10.3.0.3)
 MAC Address: 00:16:17:6D:AC:3A (MSI)
 Nmap scan report for 10.3.0.6
 MAC Address: 00:19:DB:F6:EB:B6 (Micro-star International CO.)
 Nmap scan report for deeebian.lan (10.3.0.7)

 $ awk '/MSI|Micro/ {print $3}' arp-scan.txt
 00:16:17:6D:AC:3A
 00:19:DB:F6:EB:B6

source:
http://nmap.org/book/man-host-discovery.html

You can also discover recently contacted MACs with ip(1), but then you would have to manually correlate the results with the mac-prefixes from /usr/share/nmap/nmap-mac-prefixes.

# ip neighbor
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hi @Pax how can i use this ip neighbbor – munish Apr 11 '13 at 11:09
    
Install the equivalent package of sys-apps/iproute2 on your system, but nmap is the better option for this task. – Ярослав Рахматуллин Apr 11 '13 at 12:52

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