isatapd - ISATAP client for Linux
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,
-t --ttl hoplimit
Set the tunnel hoplimit, default is 64. Specifying ’auto’ or
’inherit’ will make the tunnel inherit the ttl from the linked
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
-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
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.
Drop privileges to this user when running the solicitation loop.
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 <firstname.lastname@example.org>
Kwong-Sang Yin <email@example.com>
Fred Templin <firstname.lastname@example.org>