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FreeBSD: How to list IPv6 neighbors
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Author:  mandrei99 [ Mon Oct 06, 2014 10:00 am ]
Post subject:  FreeBSD: How to list IPv6 neighbors

FreeBSD uses ndp (Neighbor Discovery Protocol) utility to liste IPv6 information.

Quote from "man ndp":
NDP(8) FreeBSD System Manager's Manual NDP(8)

ndp -- control/diagnose IPv6 neighbor discovery protocol

ndp [-nt] hostname
ndp [-nt] -a | -c | -p
ndp [-nt] -r
ndp [-nt] -H | -P | -R
ndp [-nt] -A wait
ndp [-nt] -d hostname
ndp [-nt] -f filename
ndp [-nt] -i interface [expressions ...]
ndp [-nt] -I [interface | delete]
ndp [-nt] -s nodename etheraddr [temp] [proxy]

The ndp utility manipulates the address mapping table used by the Neigh-
bor Discovery Protocol (NDP).

-a Dump the currently existing NDP entries. The following informa-
tion will be printed:

Neighbor IPv6 address of the neighbor.

Linklayer Address
Linklayer address of the neighbor. It could be
``(incomplete)'' when the address is not available.

Netif Network interface associated with the neighbor cache

Expire The time until expiry of the entry. The entry could
become ``permanent'', in which case it will never

S State of the neighbor cache entry, as a single letter:

N Nostate
W Waitdelete
I Incomplete
R Reachable
S Stale
D Delay
P Probe
? Unknown state (should never happen).

Flags Flags on the neighbor cache entry, in a single letter.
They are: Router, proxy neighbor advertisement (``p'').
The field could be followed by a decimal number, which
means the number of NS probes the node has sent during
the current state.

# ndp -a
Neighbor                             Linklayer Address  Netif Expire    S Flags
fe80::20c:29ff:fe2a:32ba%em1        00:0c:29:2a:32:ba   vmx1 permanent R
fe80::2e21:72ff:fec6:c188%em0       2c:21:72:c6:c1:88   vmx0 23h40m13s S R
fe80::20c:31ff:fe2a:32b0%em0        00:0c:29:2a:32:b0   vmx0 permanent R

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