[CentOS] NMAP - reveal MAC address

> This will only work on a local network: 
> once you have the IP address, you can do an arp -v
> 
> You cannot get the MAC address of a routed IP address, it only exist
on a
> local network.

Heres the code snippet I've used to walk a router's MAC table:

snmpwalk -v 1 -c public ${GWADDR} ipNetToMediaPhysAddress \
    |grep ${IPADDR} |awk '{print $4}'

${GWADDR} is your router's IP and ${IPADDR} is the target's IP.  This
allows you to qets MACs in another network.  Would probably only work
for one hop; everything I have tried it on was only a single hop away.

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