How to find out what device is on what port

TechStriker

How to find out what device is on what port on your Cisco 2950 switches.
I did show mac address table command it show vlan number, mac address, type and ports, but all ports are the gigabit link ports.

Is there CLI command which returns given a mac which port the device is connected, any help is greatly appreciated.

Thanks

Sanis4life

sh mac- | i FastEthernetx/x, or if you want to search by mac use sh mac- | i XXXX ( last 4 of MAC).

Hope that helps

TechStriker

Thanks Sanis4life for your quick response

check this

sw20-2950-#sh mac- | i 0000
vlan no 10 mac 0000.0000.0000 DYNAMIC Gi0/2

it only shows me the Gi port (Gigabitport port) for all devices connected to the switch I know this the link port but i need the switch port ie fa/10 or some thing along this lines.

do you know what the issue could be

networker050184

If its showing the MAC on an up link its probably on another switch.

Sanis4life

networker050184 wrote:

If its showing the MAC on an up link its probably on another switch.

Yes, which means you need to go to that switch and run the sh mac command from there.

APA

if it is showing you the uplink that is a pointer...... follow the uplinks to each switch until you find the actual switch port the Host is on...

If the MAC is tied to an uplink it means that switch has the learnt that the host is accessible via the uplink which is connected to another switch

Stovokor

Agreed...I had to use this to find a printer that was connected to the wrong vlan. I had to go through 3 switches that were co-located. The Unix like nature of the CLI is great.

APA

If the switch management address is on the same vlan as the users....(Not good design but most networks have this) .... Use 'show ip arp | inc (ip address of host)'

Then use the mac that is output from this command and do 'show mac address-table | inc (MAC)'

Also if you have a L3 switch just run 'traceroute mac ip (source) (dest)' and this will run a L2 traceroute from port to port....

redwarrior

If you end up doing this a lot (I do because we have NAC...I have to track down a device via MAC at least 3 times a week), I find Solarwinds's Switchport Mapper in their Engineer's toolkit a good tool to use. Yes, that probably decreases my Cisco geek score, but it does speed up my workflow.

darkuser

depends whether you know the mac or ip address
i use a combination of arp and
sh mac-address-table address xxxx.xxxx.xxxx

billyr

Cant you just use CDP for this?

TechStriker

Thanks guys for all your input, is three free open source tool which will help me manage this. I have been given mini project to create database of list of all devices on the network and it is associated switch port. We need to keep track which device is connected on what port. We have around 90 cisco 2950 and 2 L3 switch and almost 850 host on the network.

Thanks

flares2

Show CDP interface does not give MAC addresses associated to the ports, only things like line protocol up/down, encapsulation, holdtime, etc.
In terms of neighboring switches it will only show the neighboring devices, not what is on each of their ports. Plus because, TechStriker stated he is using L2 switches, there are no IPs associated to the ports.

billyr

Yes your right. I'll read the whole question next time. I thought he was after just the directly connected devices.

darkuser

that will only show you devices that speak cdp multicast

astorrs

How about a pretty Visio diagram? LANSurveyor Express is free until the end of the month:

http://www.solarwinds.com/register/index.aspx?Program=583&c=70150000000DWUM&CMP=LEC-Visio-Toolbox-HP-LSE-DL

To create a switch report you would need the full version, but the free one will create a pretty network map for you. It's not what your describing but may meet your needs (not sure how flexible the requirements are).

TechStriker

Solarwinds's Engineer's toolkit seems a good tool to use I will play around with this and see what it can do for me, thanks for all your help in this matter

Regards,

APA

Yeah Solarwinds NET is awesome kit to have

If you really want to be a smart arse configure DHCP snooping -> then run show ip dhcp snooping binding...

This output gives you MAC, IP, Inteface connected and associated other values....... Plus it's a necessity for DAI and Source-Guard

redwarrior

APA - this dhcp snooping sounds neat...would I run the show command from the switch the device is connected to, the route point for the network/Vlan, or the device handing out dhcp? This sounds like it could be handy for a number of uses.

Thanks!