NAME

       ndisc6 - ICMPv6 Neighbor Discovery tool

SYNOPSIS

       ndisc6 [-1mnqv] [-r attempts] [-s source_ip] [-w wait_ms] <IPv6 address> <iface>

DESCRIPTON

       NDisc6 is an Unix program which implements the ICMPv6 Neighbor Discovery in userland (it is normally done
       by  the  kernel).  It  is  used  to  lookup  the  link-layer address (layer 2 address, MAC in the case of
       Ethernet) of any on-link IPv6 node.

       The IPv6 address of the node must be specified, as well as the networking interface on which  to  perform
       the lookup.

OPTIONS

       -1 or --single
              Exit as soon as the first advertisement is received (default).

       -h or --help
              Display some help and exit.

       -m or --multiple
              Wait for possible duplicate advertisements and print all of them.

       -n or --numeric
              If the first parameter is not a valid IPv6 address, do not try to resolve it as a DNS hostname.

       -q or --quiet
              Only  display  link-layer address. Display nothing in case of failure.  That is mostly useful when
              calling the program from a shell script.

       -r attempts or --retry attempts
              Send ICMPv6 Neighbor Discovery that many times until a reply is received, or  abort.  By  default,
              ndisc6  will  try  3  times  before  aborting  (MAX_MULTICAST_SOLICIT and MAX_UNICAST_SOLICIT from
              RFC2461).

       -s source_ip or --source source_ip
              Specify the IPv6 address to be used as the source for the neighbor solicitation packets.

       -V or --version
              Display program version and license and exit.

       -v or --verbose
              Display verbose information. That is the default.

       -w wait_ms or --wait wait_ms
              Wait wait_ms milliseconds for a response before retrying.   By  default,  ndisc6  waits  1  second
              between each attempts (RETRANS_TIMER from RFC2461).

       If  ndisc6  does  not  receive  any  response  after the specified number of attempts waiting for wait_ms
       milliseconds each time, it will exit with code 2. On error, it exits with code  1.   Otherwise  it  exits
       with code 0. This makes it possible to use the exit code to see if a host is on-link or not.

DIAGNOSTICS

       If  you  get  no response while you know the remote host is up, it is most likely that it is not on-link,
       that is to say, you must cross one or more routers to reach it.  By  design,  IPv6  nodes  ignore  ICMPv6
       Neighbor Discovery packets received from nodes not on the same link (i.e. Ethernet segment), for the sake
       of security. Technically, that is done by ensuring that the Hop limit (TTL) is 255.

       Note that you cannot use ndisc6 to lookup the local host's link-layer address.

SECURITY

       ndisc6  should  be  setuid  root  to  allow use by non-privileged users. It will drop its root privileges
       before any attempt is made to send or receive data from the network to reduce the possible  impact  of  a
       security vulnerability.

SEE ALSO

       ping6(8), rdisc6(8), ipv6(7)

AUTHOR

       Rémi Denis-Courmont <remi at remlab dot net>

       http://www.remlab.net/ndisc6/

ndisc6                                               $Date$                                            NDISC6(8)