3 Replies Latest reply on Jun 19, 2014 12:08 PM by jayh

    SNMP equivalent of "show arp" ?

    fiberopticcoffee New Member

      Does anybody know if there is an SNMP equivalent of the "show arp" CLI command in the 3100 series routers?

      I need to get IP addresses and MAC addresses of connected LAN clients.

       

      I know this should be easy, but I'm still learning how to read MIBs. =\

       

      Thanks!

        • Re: SNMP equivalent of "show arp" ?
          jayh Hall_of_Fame

          It's a standard RFC1213 MIB.

           

          .1.3.6.1.2.1.4.22.1.2

           

          or

           

          ipNetToMediaPhysAddress

           

          OBJECT-TYPE

           

            -- FROM RFC1213-MIB, IP-MIB

            -- TEXTUAL CONVENTION PhysAddress

           

            SYNTAX OCTET STRING

            MAX-ACCESS read-write

            STATUS Mandatory

            DESCRIPTION "The media-dependent `physical' address."

           

          ::= { iso(1) org(3) dod(6) internet(1) mgmt(2) mib-2(1) ip(4)

            ipNetToMediaTable(22) ipNetToMediaEntry(1) 2 }

           

          If you know the ifIndex and IP address for which you want the MAC, then you do an snmpget of .1.3.6.1.2.1.4.22.1.2.ifIndex.ip.add.re.ss

           

          If you don't then do an snmpwalk of  .1.3.6.1.2.1.4.22.1.2  which will return all entries.

           

          The number before the dot immediately before the first octet of the IP address in an snmpwalk is the interface index on which the ARP entry was learned.  You can match this to an interface description with

           

          ifDescr.[number]

          or

          .1.3.6.1.2.1.2.2.1.2.[number]

           

          Where [number] is the number before the IP address.

          • Re: SNMP equivalent of "show arp" ?
            fiberopticcoffee New Member

            That's fantastic, the haze is becoming clearer,  thanks a ton!

            This actually also solves my other issue, making sure devices are on the right interface for their VLAN.

            Good stuff!