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NAME

ndp — control/diagnose IPv6 Neighbor Discovery Protocol (NDP)

SYNOPSIS

DESCRIPTION

The ndp command manipulates the address mapping table used by the Neighbor Discovery Protocol (NDP).

-A wait

Repeat -a (dump NDP entries) every wait seconds.

-a

Dump the currently existing NDP entries. The following information will be printed:

Neighbor

The IPv6 address of the neighbor.

Linklayer Address

The linklayer address of the neighbor. If the address is not available, it will be displayed as “(incomplete)”.

Netif

The network interface associated with the neighbor cache entry.

Expire

The time until expiry of the entry. If the entry is marked “permanent”, it will never expire.

S

The state of the neighbor cache entry, as a single letter:

D

Delay

I

Incomplete

N

Nostate

P

Probe

R

Reachable

S

Stale

W

Waitdelete

?

Unknown state (should never happen).

Flags

Flags on the neighbor cache entry, in a single letter. They are: local (‘l’), Router (‘R’) and proxy neighbor advertisement (‘p’). This field may be followed by a decimal number, representing the number of NS probes the node has sent during the current state.

-c

Erase all the NDP entries.

-d hostname

Delete the specified NDP entry.

-f filename

Parse entries from file to be inserted in the neighbor cache. See the -s option for a description of the file format.

-H

Harmonize consistency between the routing table and the default router list; install the top entry of the list into the kernel routing table.

-i interface [flag ...]

View ND information for the specified interface. If additional arguments are given, ndp sets or clears the specified flags for the interface. Each flag should be separated by whitespace or tab characters. Possible flags are as follows. All of the flags can begin with the special character ‘-’, which means the flag should be cleared. Note that -- would be needed before -foo in this case.

nud

Turn on or off NUD (Neighbor Unreachability Detection) on the interface. NUD is usually turned on by default.

accept_rtadv

Specify whether or not to accept Router Advertisement messages received on the interface. Note that the kernel does not accept Router Advertisement messages unless the interface is configured for inet6 autoconfiguration.

-n

Do not try to resolve numeric addresses to hostnames.

-P

Flush all the entries in the prefix list.

-p

Show the prefix list.

-R

Flush all the entries in the default router list.

-r

Show the default router list.

-s nodename ether_addr [temp] [proxy]

Register an NDP entry for the node called nodename with the Ether address ether_addr. The Ethernet address is given as six hexadecimal bytes separated by colons. The entry will be permanent unless the word temp is given in the command. If the word proxy is given, this system will act as an ND Proxy server, responding to requests for nodename even though the node address is not its own.

-t

Print a timestamp on each entry, making it possible to merge output with tcpdump(8). Most useful when used with -A.

-V rdomain

Set the routing domain to be used. The default is 0.

EXIT STATUS

The ndp utility exits 0 on success, and >0 if an error occurs.

SEE ALSO

ip6(4), sysctl.conf(5), arp(8), sysctl(8), tcpdump(8)

HISTORY

The ndp command first appeared in the WIDE Hydrangea IPv6 protocol stack kit.