isatapd - ISATAP client for Linux
] [ --link device
] [ router
] [ ...
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.
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 or 'auto' , 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 bytes for the tunnel device, minimum
is 1280. If unspecified, 'auto' or 0, the kernel will choose the
MTU, 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 device.
- -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 or interval is 'auto' , the interval will
be 80 of the router's lifetime. Can be used to force solicitations at a
- -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
- -v --verbose
- increase verbosity
- -q --quiet
- decrease verbosity
- -h --help
- print usage
- print version
On success zero
is returned, otherwise a non-zero
- Force sending router solicitations and recreate the tunnel,
- SIGINT SIGTERM
- Gracefully shut down tunnel device and terminate.
logs to stderr when run in foreground and to syslog
using the facility LOG_DAEMON
. Verbosity can be controlled with the
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>