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NAME    [Toc]    [Back]

     routed - network RIP and router discovery routing daemon

SYNOPSIS    [Toc]    [Back]

     routed [-sqdghmpAt] [-T tracefile] [-F  net[/mask[,metric]]]
[-P parms]

DESCRIPTION    [Toc]    [Back]

     routed  is  a daemon invoked at boot time to manage the network routing tables.
  It uses  Routing  Information  Protocol,  RIPv1  (RFC
1058), RIPv2 (RFC
     1723),  and Internet Router Discovery Protocol (RFC 1256) to
maintain the
     kernel routing table.  The RIPv1 protocol is  based  on  the
     4.3BSD daemon.

     It  listens  on  the  udp(4) socket for the route(8) service
     services(5)) for Routing Information Protocol  packets.   It
also sends and
     receives  multicast  Router Discovery ICMP messages.  If the
host is a
     router, routed periodically supplies copies of  its  routing
tables to any
     directly  connected  hosts and networks.  It also advertises
or solicits
     default routes using Router Discovery ICMP messages.

     When started (or when a network interface  is  later  turned
on), routed uses
 an AF_ROUTE address family facility to find those directly connected
     interfaces configured into the system and marked ``up''.  It
adds necessary
  routes for the interfaces to the kernel routing table.
Soon after
     being first started, and provided there is at least one  interface on
     which  RIP has not been disabled, routed deletes all pre-existing nonstatic
 routes in the kernel table, except those marked  with
 flag (see route(4)), i.e. routes that have been inserted
by bgpd(8).
     Static routes in the kernel table are preserved and included
in RIP responses
 if they have a valid RIP metric (see route(8)).

     If  more  than  one  interface  is present (not counting the
loopback interface),
 it is assumed that the host  should  forward  packets
among the connected
  networks.   After  transmitting  a  RIP  request and
Router Discovery
     Advertisements or Solicitations on a new interface, the daemon enters a
     loop, listening for RIP request and response and Router Discover packets
     from other hosts.

     When a request packet is received, routed formulates a reply
based on the
     information maintained in its internal tables.  The response
packet generated
 contains a list of known routes, each marked  with  a
"hop count"
     metric  (a count of 16 or greater is considered "infinite").
     metrics reflect the metric associated  with  interface  (see
     so setting the metric on an interface is an effective way to
steer traffic.

     Responses do not contain routes with a first hop on the  requesting network
  to  implement  in  part  split-horizon.  Requests from
query programs
     such as rtquery(8) are answered with the complete table.

     The routing table maintained by the  daemon  includes  space
for several
     gateways for each destination to speed recovery from a failing router.
     RIP response packets received are used to update the routing
tables provided
  they are from one of the several currently recognized
gateways or
     advertise a better metric than at least one of the  existing

     When  an update is applied, routed records the change in its
own tables
     and updates the kernel routing table if the  best  route  to
the destination
     changes.  The change in the kernel routing table is reflected in the next
     batch of response packets sent.  If the next response is not
     for a while, a flash update response containing only recently changed
     routes is sent.

     In addition to processing incoming packets, routed also  periodically
     checks  the routing table entries.  If an entry has not been
updated for 3
     minutes, the entry's metric is set to  infinity  and  marked
for deletion.
     Deletions  are  delayed  until the route has been advertised
with an infinite
  metric  to  ensure  the  invalidation  is   propagated
throughout the local
     internet.  This is a form of poison reverse.

     Routes  in  the  kernel table that are added or changed as a
result of ICMP
     Redirect messages are deleted  after  a  while  to  minimize
     When  a  TCP  connection suffers a timeout, the kernel tells
routed, which
     deletes all redirected routes through the gateway  involved,
advances the
     age of all RIP routes through the gateway to allow an alternate to be
     chosen, and advances the age of any relevant Router  Discovery Protocol
     default routes.

     Hosts  acting  as  internetwork  routers gratuitously supply
their routing
     tables every 30 seconds to all directly connected hosts  and
     These  RIP  responses  are  sent to the broadcast address on
nets that support
 broadcasting, to the destination address  on  point-topoint links,
     and to the router's own address on other networks.  If RIPv2
is enabled,
     multicast packets are sent on interfaces that support multicasting.

     If  no  response is received on a remote interface, if there
are errors
     while sending responses, or if there are  more  errors  than
input or output
     (see  netstat(1)),  then the cable or some other part of the
interface is
     assumed to be disconnected or broken, and routes are adjusted appropriately.

     The Internet Router Discovery Protocol is handled similarly.
When the
     daemon is supplying RIP routes, it also listens  for  Router
Discovery Solicitations
  and sends Advertisements.  When it is quiet and
only listening
 to other RIP routers, it sends Solicitations and listens
for Advertisements.
   If  it  receives a good Advertisement, it stops
listening for
     broadcast or multicast RIP responses.  It tracks several advertising
     routers  to  speed recovery when the currently chosen router
dies.  If all
     discovered routers disappear, the daemon  resumes  listening
to RIP responses.

     While  using Router Discovery (which happens by default when
the system
     has a single network interface and a Router Discover  Advertisement is received),
 there is a single default route and a variable number of redirected
 host routes in the kernel table.

     The Router Discover standard  requires  that  advertisements
have a default
     "lifetime"  of 30 minutes.  That means should something happen, a client
     can be without a good route for 30 minutes.  It  is  a  good
idea to reduce
     the  default to 45 seconds using -P rdisc_interval=45 on the
command line
     or rdisc_interval=45 in the /etc/gateways file.

     See the pm_rdisc facility described below to support  "legacy" systems
     that can handle neither RIPv2 nor Router Discovery.

     By  default, neither Router Discovery advertisements nor solicitations are
     sent over point to point links (e.g., PPP).

     The options are as follows:

     -s      Forces routed to supply routing  information.   This
is the default
             if  multiple network interfaces are present on which
RIP or Router
             Discovery have not been disabled, and if the  kernel
switch ipforwarding=1.

     -q      Opposite of the -s option.

     -d       Do not run in the background.  This option is meant
for interactive

     -g      Used on internetwork routers to offer a route to the
             destination.   It  is  equivalent to -F 0/0,1 and is
present mostly
             for historical  reasons.   A  better  choice  is  -P
pm_rdisc on the
             command  line or pm_rdisc in the /etc/gateways file,
since a larger
 metric will be used, reducing the spread  of  the
             dangerous  default route.  This is typically used on
a gateway to
             the Internet, or on  a  gateway  that  uses  another
routing protocol
             whose   routes  are  not  reported  to  other  local
routers.  Notice
             that because a metric of 1 is used, this feature  is
             It  is  more  commonly  accidentally  used to create
chaos with a
             routing loop than to solve problems.

     -h      Causes host or point-to-point routes to not  be  advertised, provided
 there is a network route going the same direction.  That is
             a limited kind of aggregation.  This option is  useful on gateways
             to  Ethernets  that have other gateway machines connected with
             point-to-point links such as SLIP.

     -m      Causes the machine to advertise a host or  point-topoint route to
             its  primary interface.  It is useful on multi-homed
machines such
             as NFS servers.  This option should not be used  except when the
             cost of the host routes it generates is justified by
the popularity
 of the server.  It is effective  only  when  the
machine is supplying
  routing  information,  because there is more
than one interface.
  The -m option overrides the -q option to  the
limited extent
 of advertising the host route.

     -A      Do not ignore RIPv2 authentication if we do not care
about RIPv2
             authentication.  This option is required for conformance with RFC
             1723.   However,  it makes no sense and breaks using
RIP as a discovery
 protocol to ignore  all  RIPv2  packets  that
carry authentication
 when this machine does not care about authentication.

     -T tracefile
             Increases the debugging level  to  at  least  1  and
causes debugging
             information  to be appended to the trace file.  Note
that because
             of security concerns, it is wisest to not run routed
             with tracing directed to a file.

     -t      Increases the debugging level, which causes more information to
             be logged on the  tracefile  specified  with  -T  or
standard out.
             The  debugging  level  can be increased or decreased
with the
             SIGUSR1 or SIGUSR2 signals or  with  the  rtquery(8)

     -F net[/mask][,metric]
             Minimize routes in transmissions via interfaces with
             that match net/mask, and synthesizes a default route
to this machine
  with the metric.  The intent is to reduce RIP
traffic on
             slow, point-to-point links such as PPP links by  replacing many
             large  UDP packets of RIP information with a single,
small packet
             containing a "fake" default route.  If metric is absent, a value
             of  14  is assumed to limit the spread of the "fake"
default route.
             This is a dangerous feature that when used carelessly can cause
             routing  loops.   Notice also that more than one interface can
             match the specified network number  and  mask.   See
also -g.

     -P parms
             Equivalent to adding the parameter line parms to the
             /etc/gateways file.

     Any other argument supplied is interpreted as the name of  a
file in which
     the actions of routed should be logged.  It is better to use
-T instead
     of appending the name of the trace file to the command.

     routed also supports the  notion  of  "distant"  passive  or
active gateways.
     When  routed  is started, it reads the file /etc/gateways to
find such distant
 gateways which may not be located using  only  information from a
     routing  socket,  to  discover if some of the local gateways
are passive,
     and to obtain other parameters.  Gateways specified in  this
manner should
     be marked passive if they are not expected to exchange routing information,
 while gateways marked active should be willing to  exchange RIP
     packets.   Routes  through passive gateways are installed in
the kernel's
     routing tables once upon startup and  are  not  included  in
transmitted RIP

     Distant active gateways are treated like network interfaces.
RIP responses
 are sent to the distant active gateway.  If  no  responses are received,
  the  associated  route  is  deleted from the kernel
table and RIP responses
 advertised via other  interfaces.   If  the  distant
gateway resumes
     sending RIP responses, the associated route is restored.

     Such  gateways  can  be  useful on media that do not support
broadcasts or
     multicasts but otherwise act like classic shared media  like
     such  as  some  ATM  networks.  One can list all RIP routers
reachable on the
     ATM network in /etc/gateways with a series of "host"  lines.

     Gateways  marked  external  are  also  passive,  but are not
placed in the kernel
 routing table nor are they included in routing  updates.
The function
     of external entries is to indicate that another routing process will install
 such a route if necessary, and that  alternate  routes
to that destination
  should not be installed by routed.  Such entries are
only required
     when both routers may learn of routes to the  same  destination.

     The  /etc/gateways  file  is comprised of a series of lines,
each in one of
     the following formats or consist of parameters described below:

     net  Nname[/mask]  gateway  Gname  metric  value  <passive |
active | extern>

     host Hname gateway Gname metric value <passive  |  active  |

     Nname  or  Hname  is  the name of the destination network or
host.  It may be
     a symbolic network name or an Internet address specified  in
"dot" notation
  (see  inet(3)).  (If it is a name, then it must either
be defined in
     /etc/networks or /etc/hosts,  or  named(8)  must  have  been
started before

     mask  is  an optional number between 1 and 32 indicating the
netmask associated
 with Nname.

     Gname is the name or address of the gateway to which RIP responses should
     be forwarded.

     value  is  the hop count to the destination host or network.
host hname is
     equivalent to net nname/32.

     One of the keywords passive, active or external must be present to indicate
  whether  the  gateway  should be treated as passive or
active (as described
 above), or whether the gateway is  external  to  the
scope of the
     RIP protocol.

     Lines  that start with neither "net" nor "host" must consist
of one or
     more of the following parameter settings, separated by  commas or blanks:

             Indicates  that the other parameters on the line apply to the interface
 name ifname.  This typically  is  the  first
entry in all
             lines in /etc/gateways.

             Advertises  a  route to network nname with mask mask
and the supplied
 metric (default 1).  This is useful for  filling "holes" in
             CIDR allocations.  This parameter must appear by itself on a

             Do not use this feature  unless  necessary.   It  is

             Specifies  a RIPv2 password that will be included on
all RIPv2 responses
 sent and checked on all RIPv2 responses  received.  The
             password  must  not  contain any blanks, tab characters, commas or
             `#' characters.

     no_ag   Turns off aggregation of subnets in RIPv1 and  RIPv2

             Turns  off aggregation of networks into supernets in
RIPv2 responses.

             Equivalent to no_rip no_rdisc.

     no_rip  Disables all RIP processing on the specified  interface (no RIP
             will  be  transmitted,  and any received RIP packets
will be ignored).
  If no interfaces are allowed to process RIP
             routed  acts  purely  as  a router discovery daemon.
Note that turning
 off RIP without  explicitly  turning  on  router
discovery advertisements
  with rdisc_adv or -s Causes routed to act
as a client
             router discovery daemon, not advertising.

             Causes RIPv1 received responses to be ignored.

             Causes RIPv2 received responses to be ignored.

             Turns off RIPv1 output and causes  RIPv2  advertisements to be multicast
 when possible.

             Disables the Internet Router Discovery Protocol.

             Disables the transmission of Router Discovery Solicitations.

             Specifies that Router Discovery solicitations should
be sent,
             even  on point-to-point links, which by default only
listen to
             Router Discovery messages.

             Disables the transmission of Router Discovery Advertisements.

             Specifies   that   Router  Discovery  advertisements
should be sent,
             even on point-to-point links, which by default  only
listen to
             Router Discovery messages.

             Specifies  that  Router  Discovery packets should be
broadcast instead
 of multicast.

             Sets the preference in Router  Discovery  Advertisements to the integer

             Sets  the nominal interval with which Router Discovery Advertisements
 are transmitted to N seconds and  their  lifetime to 3*N.

             Has  an  identical  effect to -F net[/mask][,metric]
with the network
 and mask coming from the specified interface.

             Similar to fake_default.  When RIPv2 routes are multicast, so
             that  RIPv1 listeners cannot receive them, this feature causes a
             RIPv1 default route to be broadcast to RIPv1 listeners.  Unless
             modified  with  fake_default,  the  default route is
broadcast with a
             metric of 14.  That serves as a "poor  man's  router

     Note  that  the netmask associated with point-to-point links
(such as SLIP
     or PPP, with the IFF_POINTOPOINT flag) is used by routed  to
infer the
     netmask used by the remote system when RIPv1 is used.

FILES    [Toc]    [Back]

     /etc/gateways  for distant gateways

SEE ALSO    [Toc]    [Back]

     icmp(4), udp(4), rtquery(8)

     Internet  Transport Protocols, XSIS 028112, Xerox System Integration

HISTORY    [Toc]    [Back]

     The routed command appeared in 4.2BSD.

BUGS    [Toc]    [Back]

     It does not always detect unidirectional failures in network
     (e.g., when the output side fails).

OpenBSD      3.6                           June      1,      1996
[ Back ]
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