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NAME    [Toc]    [Back]

     routed, rdisc -- network RIP and router discovery routing daemon

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     The routed utility 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").  Advertised
     metrics reflect the metric associated with interface (see ifconfig(8)),
     so setting the metric on an interface is an effective way to steer traffic.

     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 insure 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 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 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 kernel switch ipforwarding=1.

     -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

     -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 authentication.

     -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      display 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.

     The routed utility 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

     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 24 hours, or that was valid within 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 no RIP updates to be sent.

	     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 smaller or more negative preferences are preferred
 by clients.

	     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.

	     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"

	     causes RIP packets from that router 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.

	     causes RIP to allow ICMP Redirect messages when the system is
	     acting as a router and forwarding packets.  Otherwise, ICMP Redirect
 messages are overridden.

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

BUGS    [Toc]    [Back]

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

HISTORY    [Toc]    [Back]

     The routed utility appeared in 4.2BSD.

FreeBSD 5.2.1			 June 1, 1996			 FreeBSD 5.2.1
[ Back ]
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