RTADVD(8) | System Manager's Manual | RTADVD(8) |
rtadvd
— router
advertisement daemon
rtadvd |
[-dDfMRs ] [-c
configfile] [-F
dumpfile] [-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 configuration file does not exist altogether,
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
advertising list.
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, however, that the zero valid lifetime cannot
invalidate the autoconfigured addresses at a receiving host immediately.
According to the specification, 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 prefix information.
Moreover, if the status of an advertising interface changes,
rtadvd
will start or stop sending router
advertisements according to the latest status.
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 suppressed.
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 zero on every advertising interface.
The command line options are:
-c
-d
-D
-f
-F
rtadvd
receives signal
SIGUSR1
. The default is
/var/run/rtadvd.dump.-M
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 protocol support.-p
-R
rtadvd
with a warning message.-s
Upon receipt of signal SIGUSR1
,
rtadvd
will dump the current internal state into
/var/run/rtadvd.dump or the file specified with
option -F
.
Use SIGTERM
to kill
rtadvd
gracefully. In this case,
rtadvd
will transmit router advertisement with
router lifetime 0 to all the interfaces (in accordance with RFC2461
6.2.5).
rtadvd
dumps its
internal state.The rtadvd
utility exits 0 on
success, and >0 if an error occurs.
The rtadvd
command first appeared in the
WIDE Hydrangea IPv6 protocol stack kit.
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 the later discussion in the IETF ipng working group, all routers
should rather advertise the messages regardless of the network topology, in
order to ensure reachability.
August 27, 2011 | macOS 14.6 |