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ROUTED(8)                   System Manager's Manual                  ROUTED(8)

     routed, rdisc - network RIP and router discovery routing daemon

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

     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 reference
     4.3BSD daemon.

     It listens on the udp(4) socket for the route(8) service (see
     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 non-static routes
     in kernel table.  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
     Discovery 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").  The
     advertised metric for a route reflects the metrics associated with
     interfaces (see ifconfig(8)) through which it is received and sent, so
     setting the metric on an interface is an effective way to steer traffic.
     See also adj_inmetric and adj_outmetric parameters below.

     Responses do not include 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 gateways.

     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 scheduled
     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 black-holes.
     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 of 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 networks.
     These RIP responses are sent to the broadcast address on nets that
     support broadcasting, to the destination address on point-to-point 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

     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 listening
     to other RIP routers, it sends Solicitations and listens for
     Advertisements.  If it receives a good Advertisement and it is not multi-
     homed, 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.  It continues listening to RIP while
     using Router Discovery if multi-homed to ensure all interfaces are used.

     The Router Discovery 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.

     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.  On a host with more than one
     network interface, this default route will be via only one of the
     interfaces.  Thus, multi-homed hosts running with -q might need no_rdisc
     described below.

     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 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.

     The following options are available:

     -s      force 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 sysctl

     -q      is the opposite of the -s option.  This is the default when only
             one interface is present.  With this explicit option, the daemon
             is always in "quiet-mode" for RIP and does not supply routing
             information to other computers.

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

     -g      used on internetwork routers to offer a route to the "default"
             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
             potentially 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 dangerous.  It is more commonly accidentally used to create
             chaos with a routing loop than to solve problems.

     -h      cause 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      cause the machine to advertise a host or point-to-point 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

     -t      increase 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) command.

     -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 routinely
             with tracing directed to a file.

     -v      displays and logs the version of daemon.

     -F net[/mask][,metric]
             minimize routes in transmissions via interfaces with addresses
             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
             is 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 responses.

     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 Ethernets
     such as some ATM networks.  One can list all RIP routers reachable on the
     HIPPI or ATM network in /etc/gateways with a series of "host" lines.
     Note that it is usually desirable to use RIPv2 in such situations to
     avoid generating lists of inferred host routes.

     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 other 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 two formats or consist of parameters described later.
     Blank lines and lines starting with '#' are comments.

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

     host Hname gateway Gname metric value <passive | active | extern>

     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 routed.)

     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.

     As can be seen when debugging is turned on with -t, such lines create
     pseudo-interfaces.  To set parameters for remote or external interfaces,
     a line starting with if=alias(Hname), if=remote(Hname), etc. should be

     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.

             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
             line.  The network number must specify a full, 32-bit value, as
             in instead of 192.0.2.

             Do not use this feature unless necessary.  It is dangerous.

             specifies that netmask of the network of which nname/mask1 is a
             subnet should be mask2.  For example ripv1_mask=,27
             marks as a subnet of instead of
     It is better to turn on RIPv2 instead of using
             this facility, for example with ripv2_out.

             specifies a RIPv2 cleartext password that will be included on all
             RIPv2 responses sent, and checked on all RIPv2 responses
             received.  Any blanks, tab characters, commas, or '#', '|', or
             NULL characters in the password must be escaped with a backslash
             (\).  The common escape sequences \n, \r, \t, \b, and \xxx have
             their usual meanings.  The KeyID must be unique but is ignored
             for cleartext passwords.  If present, start and stop are
             timestamps in the form year/month/day@hour:minute.  They specify
             when the password is valid.  The valid password with the most
             future is used on output packets, unless all passwords have
             expired, in which case the password that expired most recently is
             used, or unless no passwords are valid yet, in which case no
             password is output.  Incoming packets can carry any password that
             is valid, will be valid within the next 24 hours, or that was
             valid within the preceding 24 hours.  To protect the secrets, the
             passwd settings are valid only in the /etc/gateways file and only
             when that file is readable only by UID 0.

             specifies a RIPv2 MD5 password.  Except that a KeyID is required,
             this keyword is similar to passwd.

     no_ag   turns off aggregation of subnets in RIPv1 and RIPv2 responses.

             turns off aggregation of networks into supernets in RIPv2

             marks the interface to not be advertised in updates sent via
             other interfaces, and turns off all RIP and router discovery
             through the interface.

     no_rip  disables all RIP processing on the specified interface.  If no
             interfaces are allowed to process RIP packets, 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 RIPv2 packets to be broadcast instead of multicast.

             causes RIPv1 received responses to be ignored.

             causes RIPv2 received responses to be ignored.

             turns on RIPv2 output and causes RIPv2 advertisements to be
             multicast when possible.

     ripv2   is equivalent to no_ripv1_in and no_ripv1_out.  This enables

             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
             optionally signed integer N.  The default preference is 0.
             Default routes with larger preferences are preferred by clients.

             sets the nominal interval with which Router Discovery
             Advertisements are transmitted to N seconds and their lifetime to

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

             is 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 discovery"

             adjusts the hop count or metric of received RIP routes by delta.
             The metric of every received RIP route is increased by the sum of
             two values associated with the interface.  One is the
             adj_inmetric value and the other is the interface metric set with

             adjusts the hop count or metric of advertised RIP routes by
             delta.  The metric of every received RIP route is increased by
             the metric associated with the interface by which it was
             received, or by 1 if the interface does not have a non-zero
             metric.  The metric of the received route is then increased by
             the adj_outmetric associated with the interface.  Every
             advertised route is increased by a total of four values, the
             metric set for the interface by which it was received with
             ifconfig(8), the adj_inmetric delta of the receiving interface,
             the metric set for the interface by which it is transmitted with
             ifconfig(8), and the adj_outmetric delta of the transmitting

             causes RIP packets from router rname and other routers named in
             other trust_gateway keywords to be accepted, and packets from
             other routers to be ignored.  If networks are specified, then
             routes to other networks will be ignored from that router.

             allows the kernel to listen ICMP Redirect messages when the
             system is acting as a router and forwarding packets.  Otherwise,
             ICMP Redirect messages are overridden and deleted when the system
             is acting as a router.

     /etc/gateways  for distant gateways

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

     Internet Transport Protocols, XSIS 028112, Xerox System Integration

     The routed command appeared in 4.2BSD.

     It does not always detect unidirectional failures in network interfaces,
     for example, when the output side fails.

NetBSD 10.99                     May 17, 2004                     NetBSD 10.99