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RTADVD(8) NetBSD System Manager's Manual RTADVD(8)
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rtadvd -- router advertisement daemon
rtadvd [-CDdfRs] [-c configfile] [-M ifname] [-p pidfile] interface ...
rtadvd sends router advertisement packets to the specified interfaces.
The program will daemonize itself on invocation. It will then send
router advertisement packets periodically, as well as in response to
router solicitation messages sent by end hosts.
Router advertisements can be configured on a per-interface basis, as
described in rtadvd.conf(5).
If there is no configuration file entry for an interface, or if the con-
figuration file does not exist at all, rtadvd sets all the parameters to
their default values. In particular, rtadvd reads all the interface
routes from the routing table and advertises them as on-link prefixes.
rtadvd also watches the routing table. If an interface direct route is
added on an advertising interface and no static prefixes are specified by
the configuration file, rtadvd adds the corresponding prefix to its
Similarly, when an interface direct route is deleted, rtadvd will start
advertising the prefixes with zero valid and preferred lifetimes to help
the receiving hosts switch to a new prefix when renumbering. Note, how-
ever, that the zero valid lifetime cannot invalidate the autoconfigured
addresses at a receiving host immediately. According to the specifica-
tion, the host will retain the address for a certain period, which will
typically be two hours. The zero lifetimes rather intend to make the
address deprecated, indicating that a new non-deprecated address should
be used as the source address of a new connection. This behavior will
last for two hours. Then rtadvd will completely remove the prefix from
the advertising list, and succeeding advertisements will not contain the
Moreover, if the status of an advertising interface changes, rtadvd will
start or stop sending router advertisements according to the latest sta-
The -s option may be used to disable this behavior; rtadvd will not watch
the routing table and the whole functionality described above will be
Basically, hosts MUST NOT send Router Advertisement messages at any time
(RFC 2461, Section 6.2.3). However, it would sometimes be useful to
allow hosts to advertise some parameters such as prefix information and
link MTU. Thus, rtadvd can be invoked if router lifetime is explicitly
set to zero on every advertising interface.
The command line options are:
-C Don't expire the existing configuration on receipt of SIGHUP.
This option is only intended to aid the testing of clients that
consume Router Advertisement messages.
Specify an alternate location, configfile, for the configuration
file. By default, /etc/rtadvd.conf is used.
-D Instead of printing errors using syslog(3) send them to stderr.
Also when poll(2) fails, exit instead of retrying.
-d Print debugging information. Repeating this option, adds more
-f Foreground mode (useful when debugging). Log messages will be
dumped to stderr when this option is specified.
Specify an interface to join the all-routers site-local multicast
group. By default, rtadvd tries to join the first advertising
interface appearing on the command line. This option has meaning
only with the -R option, which enables routing renumbering proto-
Specify an alternate location, pidfile, for the PID file. By
default, /var/run/rtadvd.pid is used.
-R Accept router renumbering requests. If you enable it, an
ipsec(4) setup is suggested for security reasons. This option is
currently disabled, and is ignored by rtadvd with a warning mes-
-s Do not add or delete prefixes dynamically. Only statically con-
figured prefixes, if any, will be advertised.
Use SIGHUP to reload the configuration file /etc/rtadvd.conf. If an
invalid parameter is found in the configuration file upon the reload, the
entry will be ignored and the old configuration will be used. When
parameters in an existing entry are updated and the -C flag is not used,
rtadvd will send Router Advertisement messages with the old configuration
but zero router lifetime to the interface first, and then start to send a
Upon receipt of signal SIGUSR1, rtadvd will dump the current internal
state into /var/run/rtadvd.dump.
Use SIGTERM to kill rtadvd gracefully. In this case, rtadvd will trans-
mit router advertisement with router lifetime 0 to all the interfaces (in
accordance with RFC 2461 6.2.5).
/etc/rtadvd.conf The default configuration file.
/var/run/rtadvd.pid Contains the PID of the currently running rtadvd.
/var/run/rtadvd.dump The file in which rtadvd dumps its internal
The rtadvd utility exits 0 on success, and >0 if an error occurs.
The rtadvd command first appeared in the WIDE Hydrangea IPv6 protocol
There used to be some text that recommended users not to let rtadvd
advertise Router Advertisement messages on an upstream link to avoid
undesirable icmp6(4) redirect messages. However, based on later discus-
sion in the IETF IPng working group, all routers should rather advertise
the messages regardless of the network topology, in order to ensure
NetBSD 9.1 November 11, 2019 NetBSD 9.1