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Mac to IP recognition in Cisco Switch

Unanswered Question
Nov 27th, 2015
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Dear All

Is there anyway to get IP address against the MAC address learnt by switch? Any protocol or any other stuff to be installed on switch to serve this purpose?


Regards

Jahanzeb

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Mark Malone Fri, 11/27/2015 - 06:01
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    2017 LAN

Hey to resolve a mac to an ip its arp so the devbice needs to be layer 3, layer 2 devices dont arp so you go to the device which is doing your routing on the network , that device will contain an arp table that maps to the ips, a ;layer 2 device cannot resolve an arp to mac


example to get ip from mac (has to be layer 3 capable device and routing enabled)

CORE#sh mac address-table address 001e.149c.92c1

Legend: * - primary entry
        age - seconds since last seen
        n/a - not available
        S - secure entry
        R - router's gateway mac address entry
        D - Duplicate mac address entry

Displaying entries from standby supervisor:

     vlan   mac address    type   learn    age                 ports
----+----+---------------+-------+-----+----------+-----------------------------
*     151 001e.149c.92c1  dynamic  Yes        0     Po127


Displaying entries from active supervisor:

     vlan   mac address    type   learn    age                 ports
----+----+---------------+-------+-----+----------+-----------------------------
*     151 001e.149c.92c1  dynamic  Yes        0     Po127


CORE#sh ip arp 001e.149c.92c1
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  149.199.151.249        91   001e.149c.92c1  ARPA   Vlan151

jahanzeb.feroze Sun, 11/29/2015 - 21:03
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Hi Mark,


Where is the IP address in your given example? Cant get it


Will you please expalin in detail to me ? Will be thanful.

Mark Malone Mon, 11/30/2015 - 00:18
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sorry im not sure i get you the ip is in the show ip arp output when you check the mac adfdress againt it , go to your layer 3 device and run that command with your mac address in its place an it will provide the ip address mapped against it

so below mac 001e.149c.92c1 is equal to ip address 149.199.151.249


CORE#sh ip arp 001e.149c.92c1
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  149.199.151.249        91   001e.149c.92c1  ARPA   Vlan151



Metin Ozturk Fri, 11/27/2015 - 07:02
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Mark explain it perfect. 

You can also use 3rd party mac address discovery tools like Solarwinds to find the ip address.  

preeth puliyasseri Sun, 11/29/2015 - 23:41
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Follow what Mark told and can get Mac to Ip details from Switch itself.

I am using angry Ip scanner for finding MAC to IP details within LAN.

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