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       isatapd - ISATAP client for Linux


       isatapd --help
       isatapd [ --daemon ] [ --link device ] [ options ] [ router ] [ ... ]


       isatapd  is a userspace program or daemon that sets up and maintains an
       ISATAP client tunnel by using the kernels  ISATAP  capabilities,  first
       introduced with 2.6.25.

       The  program  will  create the tunnel, periodically query the specified
       routers, add them to the potential router list , send  periodic  router
       solicitations  and  parse  router  advertisements.  isatapd will try to
       keep the tunnel up and running, even if the network topology changes.

       See NOTES below for more information


       -n --name name
              Name of the tunnel interface. Default is is0.

       -l --link device
              Tunnel link device. If specified, tunnel will be  restricted  to
              that   device,  allowing  multiple  instances  of  isatapd  with
              different tunnels. The tunnel can only exist as long as the link
              device is up and has a IPv4 address configured.

              If  unspecified,  the  outgoing IPv4 address will be guessed for
              the first router and the tunnel created accordingly. The  tunnel
              device  will  only  created,  if there is a possible IPv4 source
              address to reach the first router.

       -m --mtu bytes
              Sets the MTU to value for the tunnel device, minimum is 1280. If
              unspecified,  the  kernel  will  choose  the  MTU automatically,
              usually 1480.

       -t --ttl hoplimit
              Set the tunnel hoplimit, default is  64.  Specifying  ’auto’  or
              ’inherit’  will  make the tunnel inherit the ttl from the linked

       -N --nopmtudisc
              Disable (IPv4) Path MTU Discovery on this tunnel.  For  this  to
              work  --ttl  has  to  be  set  to  inherit. Default: do Path MTU
              Discovery to reduce redundant fragmentation.

       -r --router router
              Set a potential router.  isatapd will resolv the  hostname,  add
              the   IPv4   address   to  the  PRL  and  send  periodic  router
              solicitation  messages.  Up  to  10  potential  routers  can  be
              specified, the default is the unqualified domainname "isatap".

       -i --interval seconds
              Default  interval  to  send  router solicitations. If the router
              lifetime is lower, the interval  will  be  80  of  the  router´s
              lifetime.  Can  be  used  to  force  solicitations  at a shorter

              Default: auto

       -D --check-dns seconds
              Interval to perform DNS resolution of configured routers and  to
              recreate the PRL, if necessary. Set to 0 to disable.

              Default: 3600 sec = 1 hour

       -d --daemon
              fork to background. No logging is available yet.

       -p --pid file
              Store  the pid as plaintext to file. The pid file will be write-
              locked to prevent multiple running instances. Useful for scripts
              and when running isatapd as a daemon.

       --user username
              Drop privileges to this user when running the solicitation loop.

              Default: nobody

       -v --verbose
              increase verbosity

       -q --quiet
              decrease verbosity

       -h --help
              print usage

              print version


       On success zero is returned, otherwise a non-zero value is returned.


       SIGHUP Force sending router solicitations and recreate the  tunnel,  if

              Gracefully shut down tunnel device and terminate.


       isatapd  logs  to stderr when run in foreground and to syslog(3), using
       the facility LOG_DAEMON. Verbosity can be controlled with the -v and -q


       Network  data  will  be  processed  by  isatapd  with  privileges of an
       unprivileged user to minimize impact of bugs in the networking code. To
       create and maintain the tunnel device, root privileges are necessary.

       Whenever  the tunnel link interface goes down or the source address for
       the local tunnel endpoint changes, the tunnel device will be  destroyed
       and recreated, if possible. Note that till then your tunnel might be in
       a unusable state.


       Sascha Hlusiak <>

       Kwong-Sang Yin <>

       Fred Templin <>


       ip(8) syslog-ng(8)