in.rdisc - network router discovery daemon


SYNOPSIS

       in.rdisc [ -sfa ]

       in.rdisc -r [ -p preference ] [ -T interval ]


DESCRIPTION

       iinn..rrddiisscc  implements  the  ICMP  router discover protocol.
       The first form of the command is used  on  hosts  and  the
       second  form  is  used  on routers.  On a host iinn..rrddiisscc is
       invoked at boot  time  to  populate  the  network  routing
       tables  with  default  routes.   On  a  router  it is also
       invoked at boot time in order  to  start  advertising  the
       router to all the hosts.

   Host (First Form)
       On  a  host  iinn..rrddiisscc listens on the AALLLL_HHOOSSTTSS (224.0.0.1)
       multicast  address  for  RROOUUTTEERR_AADDVVEERRTTIISSEE  messages   from
       routers. The received messages are handled by first ignor­
       ing those listed router addresses with which the host does
       not  share  a  network.  Among the remaining addresses the
       ones with the highest preference are selected  as  default
       routers and a default route is entered in the kernel rout­
       ing table for each one of them.

       Optionally, iinn..rrddiisscc can  avoid  waiting  for  routers  to
       announce  themselves by sending out a few RROOUUTTEERR_SSOOLLIICCIITTAA­­
       TTIIOONN messages to  the  AALLLL_RROOUUTTEERRSS  (224.0.0.2)  multicast
       address when it is started.

       A  timer  is  associated  with each router address and the
       address will no longer be considered for inclusion in  the
       the  routing  tables  if  the  timer  expires before a new
       advertise  message  is  received  from  the  router.   The
       address  will  also  be excluded from consideration if the
       host receives an advertise  message  with  the  preference
       being maximally negative.

   Router (Second Form)
       When iinn..rrddiisscc is started on a router, it uses the SSIIOOCCGGIIFF­­
       CCOONNFF ioctl(2) to find the interfaces configured  into  the
       system  and  it starts listening on the AALLLL_RROOUUTTEERRSS multi­
       cast address on all the interfaces that support multicast.
       It sends out advertise messages to the AALLLL_HHOOSSTTSS multicast
       address advertising all  its  addresses.   A  few  initial
       advertise  messages  are sent out during the first 30 sec­
       onds and after that it will  transmit  advertise  messages
       approximately every 600 seconds.

       When  iinn..rrddiisscc receives a solicitation message it sends an
       advertise message to the host that sent  the  solicitation
       message.

       advertise message with the preference being maximally neg­
       ative.


OPTIONS

       -a             Accept  all  routers  independently  of the
                      preference they  have  in  their  advertise
                      messages.   Normally  in.rdisc only accepts
                      (and enters in the kernel  routing  tables)
                      the  router  or  routers  with  the highest
                      preference.

       -f             Run in.rdisc forever even if no routers are
                      found.   Normally  in.rdisc  gives up if it
                      has  not  received  any  advertise  message
                      after  after  soliciting  three  times,  in
                      which case it exits with  a  non-zero  exit
                      code.   If -f is not specified in the first
                      form then -s must be specified.

       -p preference  Set  the  preference  transmitted  in   the
                      solicitation   messages.   The  default  is
                      zero.

       -r             Act as a router as opposed to a host.

       -s             Send three solicitation messages  initially
                      to  quickly  discover  the routers when the
                      system is booted.   When  -s  is  specified
                      in.rdisc exits with a non-zero exit code if
                      it can not find any routers.  This  can  be
                      overridden with the -f option.

       -T interval    Set  the  interval between transmitting the
                      advertise messages.  The  default  time  is
                      600 seconds.


SEE ALSO

       in.routed(8C) ioctl(2), icmp(7), inet(7)

       Deering,  S.E.,ed  ``ICMP Router Discovery Messages,'' RFC
       1256, Network Information Center, SRI International, Menlo
       Park, Calif., September 1991.


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