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30 .\" @(#)routed.8 8.2 (Berkeley) 12/11/93
39 .Nd network RIP and router discovery routing daemon
46 .Ar net Ns Op /mask Ns Op ,metric
52 utility is a daemon invoked at boot time to manage the network
54 It uses Routing Information Protocol, RIPv1 (RFC\ 1058),
56 and Internet Router Discovery Protocol (RFC 1256)
57 to maintain the kernel routing table.
58 The RIPv1 protocol is based on the reference
68 for Routing Information Protocol packets.
69 It also sends and receives multicast Router Discovery ICMP messages.
70 If the host is a router,
72 periodically supplies copies
73 of its routing tables to any directly connected hosts and networks.
74 It also advertises or solicits default routes using Router Discovery
77 When started (or when a network interface is later turned on),
79 uses an AF_ROUTE address family facility to find those
80 directly connected interfaces configured into the
81 system and marked "up".
82 It adds necessary routes for the interfaces
83 to the kernel routing table.
84 Soon after being first started, and provided there is at least one
85 interface on which RIP has not been disabled,
87 deletes all pre-existing
88 non-static routes in kernel table.
89 Static routes in the kernel table are preserved and
90 included in RIP responses if they have a valid RIP -hopcount
94 If more than one interface is present (not counting the loopback interface),
95 it is assumed that the host should forward packets among the
97 After transmitting a RIP
100 Router Discovery Advertisements or Solicitations on a new interface,
101 the daemon enters a loop, listening for
102 RIP request and response and Router Discovery packets from other hosts.
108 formulates a reply based on the information maintained in its
112 packet generated contains a list of known routes, each marked
113 with a "hop count" metric (a count of 16 or greater is
114 considered "infinite").
115 The advertised metric for a route reflects the metrics associated
119 though which it is received and sent,
120 so setting the metric on an interface
121 is an effective way to steer traffic.
128 Responses do not include routes with a first hop on the requesting
129 network to implement in part
131 Requests from query programs
134 are answered with the complete table.
136 The routing table maintained by the daemon
137 includes space for several gateways for each destination
138 to speed recovery from a failing router.
141 packets received are used to update the routing tables provided they are
142 from one of the several currently recognized gateways or
143 advertise a better metric than at least one of the existing
146 When an update is applied,
148 records the change in its own tables and updates the kernel routing table
149 if the best route to the destination changes.
150 The change in the kernel routing table is reflected in the next batch of
153 If the next response is not scheduled for a while, a
155 response containing only recently changed routes is sent.
157 In addition to processing incoming packets,
159 also periodically checks the routing table entries.
160 If an entry has not been updated for 3 minutes, the entry's metric
161 is set to infinity and marked for deletion.
162 Deletions are delayed until the route has been advertised with
163 an infinite metric to ensure the invalidation
164 is propagated throughout the local internet.
168 Routes in the kernel table that are added or changed as a result
169 of ICMP Redirect messages are deleted after a while to minimize
171 When a TCP connection suffers a timeout,
174 which deletes all redirected routes
175 through the gateway involved, advances the age of all RIP routes through
176 the gateway to allow an alternate to be chosen, and advances of the
177 age of any relevant Router Discovery Protocol default routes.
179 Hosts acting as internetwork routers gratuitously supply their
180 routing tables every 30 seconds to all directly connected hosts
182 These RIP responses are sent to the broadcast address on nets that support
184 to the destination address on point-to-point links, and to the router's
185 own address on other networks.
186 If RIPv2 is enabled, multicast packets are sent on interfaces that
187 support multicasting.
189 If no response is received on a remote interface, if there are errors
190 while sending responses,
191 or if there are more errors than input or output (see
193 then the cable or some other part of the interface is assumed to be
194 disconnected or broken, and routes are adjusted appropriately.
197 .Em Internet Router Discovery Protocol
198 is handled similarly.
199 When the daemon is supplying RIP routes, it also listens for
200 Router Discovery Solicitations and sends Advertisements.
201 When it is quiet and listening to other RIP routers, it
202 sends Solicitations and listens for Advertisements.
204 a good Advertisement and it is not multi-homed,
205 it stops listening for broadcast or multicast RIP responses.
206 It tracks several advertising routers to speed recovery when the
207 currently chosen router dies.
208 If all discovered routers disappear,
209 the daemon resumes listening to RIP responses.
210 It continues listening to RIP while using Router Discovery
211 if multi-homed to ensure all interfaces are used.
213 The Router Discovery standard requires that advertisements
214 have a default "lifetime" of 30 minutes.
216 something happen, a client can be without a good route for
218 It is a good idea to reduce the default to 45
220 .Fl P Cm rdisc_interval=45
221 on the command line or
222 .Cm rdisc_interval=45
227 While using Router Discovery (which happens by default when
228 the system has a single network interface and a Router Discover Advertisement
229 is received), there is a single default route and a variable number of
230 redirected host routes in the kernel table.
231 On a host with more than one network interface,
232 this default route will be via only one of the interfaces.
233 Thus, multi-homed hosts running with
241 facility described below to support "legacy" systems
242 that can handle neither RIPv2 nor Router Discovery.
244 By default, neither Router Discovery advertisements nor solicitations
245 are sent over point to point links (e.g.\& PPP).
246 The netmask associated with point-to-point links (such as SLIP
247 or PPP, with the IFF_POINTOPOINT flag) is used by
249 to infer the netmask used by the remote system when RIPv1 is used.
251 The following options are available:
252 .Bl -tag -width indent
256 to supply routing information.
257 This is the default if multiple network interfaces are present on which
258 RIP or Router Discovery have not been disabled, and if the kernel switch
261 is the opposite of the
264 This is the default when only one interface is present.
265 With this explicit option, the daemon is always in "quiet-mode" for RIP
266 and does not supply routing information to other computers.
268 do not run in the background.
269 This option is meant for interactive use.
271 used on internetwork routers to offer a route
272 to the "default" destination.
276 and is present mostly for historical reasons.
279 on the command line or
284 since a larger metric
285 will be used, reducing the spread of the potentially dangerous
287 This is typically used on a gateway to the Internet,
288 or on a gateway that uses another routing protocol whose routes
289 are not reported to other local routers.
290 Notice that because a metric of 1 is used, this feature is
292 It is more commonly accidentally used to create chaos with a
293 routing loop than to solve problems.
295 cause host or point-to-point routes to not be advertised,
296 provided there is a network route going the same direction.
297 That is a limited kind of aggregation.
298 This option is useful on gateways to Ethernets that have other gateway
299 machines connected with point-to-point links such as SLIP.
301 cause the machine to advertise a host or point-to-point route to
302 its primary interface.
303 It is useful on multi-homed machines such as NFS servers.
304 This option should not be used except when the cost of
305 the host routes it generates is justified by the popularity of
307 It is effective only when the machine is supplying
308 routing information, because there is more than one interface.
313 option to the limited extent of advertising the host route.
315 do not ignore RIPv2 authentication if we do not care about RIPv2
317 This option is required for conformance with RFC 1723.
318 However, it makes no sense and breaks using RIP as a discovery protocol
319 to ignore all RIPv2 packets that carry authentication when this machine
320 does not care about authentication.
322 increase the debugging level, which causes more information to be logged
323 on the tracefile specified with
326 The debugging level can be increased or decreased
334 .It Fl T Ar tracefile
335 increases the debugging level to at least 1 and
336 causes debugging information to be appended to the trace file.
337 Note that because of security concerns, it is wisest to not run
339 routinely with tracing directed to a file.
341 display and logs the version of daemon.
342 .It Fl F Ar net[/mask][,metric]
343 minimize routes in transmissions via interfaces with addresses that match
345 and synthesizes a default route to this machine with the
347 The intent is to reduce RIP traffic on slow, point-to-point links
348 such as PPP links by replacing many large UDP packets of RIP information
349 with a single, small packet containing a "fake" default route.
352 is absent, a value of 14 is assumed to limit
353 the spread of the "fake" default route.
354 This is a dangerous feature that when used carelessly can cause routing
356 Notice also that more than one interface can match the specified network
361 is equivalent to adding the parameter
369 Any other argument supplied is interpreted as the name
370 of a file in which the actions of
376 appending the name of the trace file to the command.
380 utility also supports the notion of
388 is started, it reads the file
390 to find such distant gateways which may not be located using
391 only information from a routing socket, to discover if some
392 of the local gateways are
394 and to obtain other parameters.
395 Gateways specified in this manner should be marked passive
396 if they are not expected to exchange routing information,
397 while gateways marked active
398 should be willing to exchange RIP packets.
401 gateways are installed in the
402 kernel's routing tables once upon startup and are not included in
403 transmitted RIP responses.
405 Distant active gateways are treated like network interfaces.
406 RIP responses are sent
410 If no responses are received, the associated route is deleted from
411 the kernel table and RIP responses advertised via other interfaces.
412 If the distant gateway resumes sending RIP responses, the associated
415 Such gateways can be useful on media that do not support broadcasts
416 or multicasts but otherwise act like classic shared media like
417 Ethernets such as some ATM networks.
418 One can list all RIP routers reachable on the HIPPI or ATM network in
422 Note that it is usually desirable to use RIPv2 in such situations
423 to avoid generating lists of inferred host routes.
427 are also passive, but are not placed in the kernel
428 routing table nor are they included in routing updates.
429 The function of external entries is to indicate
430 that another routing process
431 will install such a route if necessary,
432 and that other routes to that destination should not be installed
435 Such entries are only required when both routers may learn of routes
436 to the same destination.
440 file is comprised of a series of lines, each in
441 one of the following two formats or consist of parameters described later.
442 Blank lines and lines starting with '#' are comments.
451 .Pf < Cm passive No \&|
462 .Pf < Cm passive No \&|
470 is the name of the destination network or host.
471 It may be a symbolic network name or an Internet address
472 specified in "dot" notation (see
474 (If it is a name, then it must either be defined in
480 must have been started before
484 is an optional number between 1 and 32 indicating the netmask associated
489 is the name or address of the gateway to which RIP responses should
493 is the hop count to the destination host or network.
497 .Cm net Ar nname/32 .
504 must be present to indicate whether the gateway should be treated as
508 (as described above),
509 or whether the gateway is
511 to the scope of the RIP protocol.
513 As can be seen when debugging is turned on with
515 such lines create pseudo-interfaces.
516 To set parameters for remote or external interfaces,
518 .Cm if=alias(Hname) ,
519 .Cm if=remote(Hname) ,
520 etc.\& should be used.
522 Lines that start with neither "net" nor "host" must consist of one
523 or more of the following parameter settings, separated by commas or
525 .Bl -tag -width indent
526 .It Cm if Ns = Ns Ar ifname
527 indicates that the other parameters on the line apply to the interface
530 .It Cm subnet Ns = Ns Ar nname Ns Oo / Ns Ar mask Oc Ns Op , Ns Ar metric
531 advertises a route to network
535 and the supplied metric (default 1).
536 This is useful for filling "holes" in CIDR allocations.
537 This parameter must appear by itself on a line.
538 The network number must specify a full, 32-bit value, as in 192.0.2.0
541 Do not use this feature unless necessary.
543 .It Cm ripv1_mask Ns = Ns Ar nname Ns / Ns Ar mask1 , Ns Ar mask2
544 specifies that netmask of the network of which
545 .Ar nname Ns / Ns Ar mask1
550 .Dq Li ripv1_mask=192.0.2.16/28,27
552 as a subnet of 192.0.2.0/27 instead of 192.0.2.0/24.
553 It is better to turn on RIPv2 instead of using this facility, for example
556 .It Cm passwd Ns = Ns Ar XXX[|KeyID[start|stop]]
557 specifies a RIPv2 cleartext password that will be included on
558 all RIPv2 responses sent, and checked on all RIPv2 responses received.
559 Any blanks, tab characters, commas, or '#', '|', or NULL characters in the
560 password must be escaped with a backslash (\\).
561 The common escape sequences \\n, \\r, \\t, \\b, and \\xxx have their
565 must be unique but is ignored for cleartext passwords.
570 are timestamps in the form year/month/day@hour:minute.
571 They specify when the password is valid.
572 The valid password with the most future is used on output packets, unless
573 all passwords have expired, in which case the password that expired most
574 recently is used, or unless no passwords are valid yet, in which case
575 no password is output.
576 Incoming packets can carry any password that is valid, will
577 be valid within the next 24 hours, or that was valid within the preceding
579 To protect the secrets, the passwd settings are valid only in the
581 file and only when that file is readable only by UID 0.
582 .It Cm md5_passwd Ns \&= Ns Ar XXX|KeyID[start|stop]
583 specifies a RIPv2 MD5 password.
586 is required, this keyword is similar to
589 turns off aggregation of subnets in RIPv1 and RIPv2 responses.
591 turns off aggregation of networks into supernets in RIPv2 responses.
593 marks the interface to not be advertised in updates sent via other
594 interfaces, and turns off all RIP and router discovery through the interface.
596 disables all RIP processing on the specified interface.
597 If no interfaces are allowed to process RIP packets,
599 acts purely as a router discovery daemon.
601 Note that turning off RIP without explicitly turning on router
602 discovery advertisements with
608 to act as a client router discovery daemon, not advertising.
610 causes RIPv2 packets to be broadcast instead of multicast.
612 causes no RIP updates to be sent.
614 causes RIPv1 received responses to be ignored.
616 causes RIPv2 received responses to be ignored.
618 turns on RIPv2 output and causes RIPv2 advertisements to be
619 multicast when possible.
627 disables the Internet Router Discovery Protocol.
629 disables the transmission of Router Discovery Solicitations.
631 specifies that Router Discovery solicitations should be sent,
632 even on point-to-point links,
633 which by default only listen to Router Discovery messages.
635 disables the transmission of Router Discovery Advertisements.
637 specifies that Router Discovery Advertisements should be sent,
638 even on point-to-point links,
639 which by default only listen to Router Discovery messages.
641 specifies that Router Discovery packets should be broadcast instead of
643 .It Cm rdisc_pref Ns \&= Ns Ar N
644 sets the preference in Router Discovery Advertisements to the optionally
647 The default preference is 0.
648 Default routes with smaller or more negative preferences are preferred by
650 .It Cm rdisc_interval Ns \&= Ns Ar N
651 sets the nominal interval with which Router Discovery Advertisements
652 are transmitted to N seconds and their lifetime to 3*N.
653 .It Cm fake_default Ns \&= Ns Ar metric
654 has an identical effect to
655 .Fl F Ar net[/mask][=metric]
656 with the network and mask coming from the specified interface.
660 When RIPv2 routes are multicast, so that RIPv1 listeners cannot
661 receive them, this feature causes a RIPv1 default route to be
662 broadcast to RIPv1 listeners.
665 the default route is broadcast with a metric of 14.
666 That serves as a "poor man's router discovery" protocol.
667 .It Cm adj_inmetric Ns \&= Ns Ar delta
668 adjusts the hop count or metric of received RIP routes by
670 The metric of every received RIP route is increased by the sum
671 of two values associated with the interface.
672 One is the adj_inmetric value and the other is the interface
675 .It Cm adj_outmetric Ns \&= Ns Ar delta
676 adjusts the hop count or metric of advertised RIP routes by
678 The metric of every received RIP route is increased by the metric
679 associated with the interface by which it was received, or by 1 if
680 the interface does not have a non-zero metric.
681 The metric of the received route is then increased by the
682 adj_outmetric associated with the interface.
683 Every advertised route is increased by a total of four
685 the metric set for the interface by which it was received with
688 .Cm adj_inmetric Ar delta
689 of the receiving interface,
690 the metric set for the interface by which it is transmitted with
693 .Cm adj_outmetric Ar delta
694 of the transmitting interface.
695 .It Cm trust_gateway Ns \&= Ns Ar rname[|net1/mask1|net2/mask2|...]
696 causes RIP packets from router
698 and other routers named in other
700 keywords to be accepted, and packets from other routers to be ignored.
701 If networks are specified, then routes to other networks will be ignored
704 allows the kernel to listen ICMP Redirect messages when the system is acting
705 as a router and forwarding packets.
706 Otherwise, ICMP Redirect messages are overridden and deleted when the
707 system is acting as a router.
710 .Bl -tag -width /etc/gateways -compact
719 .%T Internet Transport Protocols
721 .%Q Xerox System Integration Standard
728 .\" LocalWords: loopback ICMP rtquery ifconfig multicasting Solicitations RIPv
729 .\" LocalWords: netstat rdisc
731 It does not always detect unidirectional failures in network interfaces,
732 for example, when the output side fails.
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