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resolve ip address from a switch port

By michael.burgess ·
We have been using old smarthubs for the last 8 years and now just installed hp procurve switches.

Can anyone explain to me how I can resolve ip address from the switch ports. I have a switch in a bldg. and I want to know who is connect to port 30 on my switch. It's up and active but I can't identify what device is connected to it.

I have read some documentation and tried to view my arp tables but the specific port isn't listed.

I have the mac address of the device that's on the port but I am at a loss.


Is there any software or a better way of doing this.

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by superjn In reply to resolve ip address from a ...

If you go to any router on the network and show the ARP table, you should be able to resolve the MAC address to an IP. Switches do not understand IP since they work at Layer 2.

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by CG IT In reply to resolve ip address from a ...

SuperJN has it. Switches do not understand IPs only MAC addresses.

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by michael.burgess In reply to resolve ip address from a ...

We have 1 cisco router on our network and it is administered by corporate offices.

any other alternative?

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by Amjad Zoghbi In reply to resolve ip address from a ...

Hello,

It is (almost) impossible to know what IP is connected to what port on your Layer 2 switch, because, as has been said in previous posts, the switch does not actually 'see' IPs.
what you can do is disable the port (using the switch management) and ping a specific address or scan, the address that does not reply, or the one that is missing in your IP scan is the one connected to the port.

further, i need to add at this point that if it is really important to know what ip is connected to a specific socket, you should implement a documentation procedure within your enterprise to record what ip or MAC address (if using DHCP) is being connected to a port.

hope this helps.

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by galoki In reply to resolve ip address from a ...

Michael,

if you spend the money...this tool will do exactly what you are looking for. Previous posters are correct that switches talk layer 2 (mac addresses) and not layer 3, however there are tools that will resolve the ip address to a mac address and they follow the arp tables on the swithes to find the originating port. All this you can do manually, but if there is a cool tool that will do it...why bother?

http://www.solarwinds.net/Tools/Network_Discovery/Switch_Port_Mapper/index.htm

I've used this for a while and it works great...especially for the big blade switches like the 6500's and 4500's.

ron

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by michael.burgess In reply to resolve ip address from a ...

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Resolving the IP Address

by C-3PO In reply to resolve ip address from a ...

Here's a trick... assuming you are using DHCP. On the HP Procurve switch, use the "show mac-address <port>" to find the MAC addresses attached to the switch port. Have a look in DHCP and sort by the "Unique ID" field (which is the MAC address). Find the MAC and you'll have the IP address.

If you have different DHCP for different VLAN's, you can list the MAC addresses for the whole VLAN using "show mac-address VLAN <#>

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