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I am wondering if there are any Linux tools out there which might aid in identification of hosts directly connected to each other (much like Cisco Discovery Protocol on switches)?

I have found which searching. But it appears to be a dead project and the patch is only for older kernels.

I am just trying to alleviate the tedious task of ethernet interface to ARP MAC address to hostname lookup. A bonus would be something that also announced its own neighbors so you could have a 2 hop view of the rest of network.

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What's the use case here? – EEAA May 7 '12 at 22:48
To help remotely identify port to port mapping of Linux machines connected to each other without a switch. – Andy Shinn May 7 '12 at 23:14
So you have a bunch of servers connected directly? Sound very painful. – EEAA May 7 '12 at 23:43
up vote 4 down vote accepted

Are you looking for LLDP?

Agent software is out there for Linux, and many network devices support it.

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Yep, this looks like what I was after. Actually, the Intel LLDP agent doesn't provide much information at all. With some more searching about LLDP I discovered which does a simple output of the LLDP neighbors, their interface, MAC, hostname, IP address, and more. This becomes very helpful information when there are no switches to provide a MAC table. – Andy Shinn May 7 '12 at 23:52
The LLDP information also led me to which appears to be exactly what I was looking for. – Andy Shinn May 9 '12 at 16:24

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