608 lines
19 KiB
Groff
608 lines
19 KiB
Groff
.\" $NetBSD: routed.8,v 1.9 1996/09/24 16:24:21 christos Exp $
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.\"
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.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)routed.8 8.2 (Berkeley) 12/11/93
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.\"
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.Dd June 1, 1996
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.Dt ROUTED 8
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.Os BSD 4.4
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.Sh NAME
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.Nm routed
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.Nd network RIP and router discovery routing daemon
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.Sh SYNOPSIS
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.Nm
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.Op Fl sqdghmpAt
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.Op Fl T Ar tracefile
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.Oo
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.Fl F
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.Ar net Ns Op /mask Ns Op ,metric
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.Oc
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.OP Fl P Ar parms
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.Sh DESCRIPTION
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.Nm Routed
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is a dameon invoked at boot time to manage the network
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routing tables.
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It uses Routing Information Protocol, RIPv1 (RFC\ 1058),
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RIPv2 (RFC\ 1723),
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and Internet Router Discovery Protocol (RFC 1256)
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to maintain the kernel routing table.
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The RIPv1 protocol is based on the reference 4.3BSD daemon.
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.Pp
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It listens on the
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.Xr udp 4
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socket for the
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.Xr route 8
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service (see
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.Xr services 5 )
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for Routing Information Protocol packets.
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It also sends and receives multicast Router Discovery ICMP messages.
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If the host is a router,
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.Nm
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periodically supplies copies
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of its routing tables to any directly connected hosts and networks.
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It also advertise or solicits default routes using Router Discovery
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ICMP messages.
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.Pp
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When started (or when a network interface is later turned on),
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.Nm
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uses an AF_ROUTE address family facility to find those
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directly connected interfaces configured into the
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system and marked "up".
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It adds necessary routes for the interfaces
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to the kernel routing table.
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Soon after being first started, and provided there is at least one
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interface on which RIP has not been disabled,
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.Nm
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deletes all pre-existing
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non-static routes in kernel table.
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Static routes in the kernel table are preserved and
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included in RIP responses if they have a valid RIP metric
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(see
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.Xr route 8 ).
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.Pp
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If more than one interface is present (not counting the loopback interface),
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it is assumed that the host should forward packets among the
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connected networks.
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After transmitting a RIP
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.Em request
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and
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Router Discovery Advertisements or Solicitations on a new interface,
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the daemon enters a loop, listening for
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RIP request and response and Router Discover packets from other hosts.
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.Pp
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When a
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.Em request
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packet is received,
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.Nm
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formulates a reply based on the information maintained in its
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internal tables.
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The
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.Em response
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packet generated contains a list of known routes, each marked
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with a "hop count" metric (a count of 16 or greater is
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considered "infinite").
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Advertised metrics reflect the metric associated with interface
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(see
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.Xr ifconfig 8 ),
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so setting the metric on an interface
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is an effective way to steer traffic.
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.Pp
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Responses do not contain routes with a first hop on the requesting
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network to implement in part
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.Em split-horizon .
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Requests from query programs
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such as
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.Xr rtquery 8
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are answered with the complete table.
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.Pp
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The routing table maintained by the daemon
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includes space for several gateways for each destination
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to speed recovery from a failing router.
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RIP
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.Em response
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packets received are used to update the routing tables provided they are
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from one of the several currently recognized gateways or
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advertise a better metric than at least one of the existing
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gateways.
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.Pp
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When an update is applied,
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.Nm
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records the change in its own tables and updates the kernel routing table
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if the best route to the destination changes.
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The change in the kernel routing tableis reflected in the next batch of
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.Em response
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packets sent.
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If the next response is not scheduled for a while, a
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.Em flash update
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response containing only recently changed routes is sent.
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.Pp
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In addition to processing incoming packets,
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.Nm
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also periodically checks the routing table entries.
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If an entry has not been updated for 3 minutes, the entry's metric
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is set to infinity and marked for deletion.
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Deletions are delayed until the route has been advertised with
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an infinite metric to insure the invalidation
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is propagated throughout the local internet.
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This is a form of
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.Em poison reverse .
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.Pp
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Routes in the kernel table that are added or changed as a result
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of ICMP Redirect messages are deleted after a while to minimize
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.Em black-holes .
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When a TCP connection suffers a timeout,
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the kernel tells
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.Nm routed ,
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which deletes all redirected routes
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through the gateway involved, advances the age of all RIP routes through
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the gateway to allow an alternate to be chosen, and advances of the
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age of any relevant Router Discovery Protocol default routes.
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.Pp
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Hosts acting as internetwork routers gratuitously supply their
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routing tables every 30 seconds to all directly connected hosts
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and networks.
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These RIP responses are sent to the broadcast address on nets that support
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broadcasting,
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to the destination address on point-to-point links, and to the router's
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own address on other networks.
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If RIPv2 is enabled, multicast packets are sent on interfaces that
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support multicasting.
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.Pp
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If no response is received on a remote interface, if there are errors
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while sending responses,
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or if there are more errors than input or output (see
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.Xr netstat 8 ),
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then the cable or some other part of the interface is assumed to be
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disconnected or broken, and routes are adjusted appropriately.
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.Pp
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The
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.Em Internet Router Discovery Protocol
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is handled similarly.
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When the daemon is supplying RIP routes, it also listens for
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Router Discovery Solicitations and sends Advertisements.
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When it is quiet and only listening to other RIP routers, it
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sends Solicitations and listens for Advertisements.
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If it receives
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a good Advertisement, it stops listening for broadcast or multicast
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RIP responses.
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It tracks several advertising routers to speed recovery when the
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currently chosen router dies.
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If all discovered routers disappear,
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the daemon resumes listening to RIP responses.
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.Pp
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While using Router Discovery (which happens by default when
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the system has a single network interface and a Router Discover Advertisement
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is received), there is a single default route and a variable number of
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redirected host routes in the kernel table.
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.Pp
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The Router Discover standard requires that advertisements
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have a default "lifetime" of 30 minutes. That means should
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something happen, a client can be without a good route for
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30 minutes. It is a good idea to reduce the default to 45
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seconds using
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.Fl P Cm rdisc_interval=45
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on the command line or
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.Cm rdisc_interval=45
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in the
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.Pa /etc/gateways
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file.
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.Pp
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While using Router Discovery (which happens by default when
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the system has a single network interface and a Router Discover Advertisement
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is received), there is a single default route and a variable number of
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redirected host routes in the kernel table.
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.Pp
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See the
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.Cm pm_rdisc
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facility described below to support "legacy" systems
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that can handle neither RIPv2 nor Router Discovery.
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.Pp
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By default, neither Router Discovery advertisements nor solicications
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are sent over point to point links (e.g. PPP).
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.Pp
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Options supported by
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.Nm routed :
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.Bl -tag -width Ds
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.It Fl s
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this option forces
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.Nm
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to supply routing information.
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This is the default if multiple network interfaces are present on which
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RIP or Router Discovery have not been disabled, and if the kernel switch
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ipforwarding=1.
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.It Fl q
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is the opposite of the
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.Fl s
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option.
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.It Fl d
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Do not run in the background.
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This option is meant for interactive use.
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.It Fl g
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This flag is used on internetwork routers to offer a route
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to the "default" destination.
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It is equivalent to
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.Fl F
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.Cm 0/0,1
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and is present mostly for historical reasons.
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A better choice is
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.Fl P Cm pm_rdisc
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on the command line or
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.CM pm_rdisc in the
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.Pa /etc/gateways
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file.
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since a larger metric
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will be used, reducing the spread of the potentially dangerous
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default route.
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This is typically used on a gateway to the Internet,
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or on a gateway that uses another routing protocol whose routes
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are not reported to other local routers.
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Notice that because a metric of 1 is used, this feature is
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dangerous. It is more commonly accidently used to create chaos with routing
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loop than to solve problems.
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.It Fl h
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This causes host or point-to-point routes to not be advertised,
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provided there is a network route going the same direction.
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That is a limited kind of aggregation.
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This option is useful on gateways to ethernets that have other gateway
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machines connected with point-to-point links such as SLIP.
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.It Fl m
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This causes the machine to advertise a host or point-to-point route to
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its primary interface.
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It is useful on multi-homed machines such as NFS servers.
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This option should not be used except when the cost of
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the host routes it generates is justified by the popularity of
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the server.
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It is effective only when the machine is supplying
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routing information, because there is more than one interface.
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The
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.Fl m
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option overrides the
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.Fl q
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option to the limited extent of advertising the host route.
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.It Fl A
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do not ignore RIPv2 authentication if we do not care about RIPv2
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authentication.
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This option is required for conformance with RFC 1723.
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However, it makes no sense and breaks using RIP as a discovery protocol
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to ignore all RIPv2 packets that carry authentication when this machine
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does not care about authentication.
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.It Fl T Ar tracefile
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increases the debugging level to at least 1 and
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causes debugging information to be appended to the trace file.
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Note that because of security concerns, it is wisest to not run
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.Nm routed
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routinely with tracing directed to a file.
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.It Fl t
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increases the debugging level, which causes more information to be logged
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on the tracefile specified with
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.Fl T
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or standard out.
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The debugging level can be increased or decreased
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with the
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.Em SIGUSR1
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or
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.Em SIGUSR2
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signals or with the
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.Cm rtquery
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command.
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.It Fl F Ar net[/mask][,metric]
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minimize routes in transmissions via interfaces with addresses that match
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.Em net/mask ,
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and synthesizes a default route to this machine with the
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.Em metric .
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The intent is to reduce RIP traffic on slow, point-to-point links
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such as PPP links by replacing many large UDP packets of RIP information
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with a single, small packet containing a "fake" default route.
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If
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.Em metric
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is absent, a value of 14 is assumed to limit
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the spread of the "fake" default route.
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This is a dangerous feature that when used carelessly can cause routing
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loops.
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Notice also that more than one interface can match the specified network
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number and mask.
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See also
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.Fl g .
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.It Fl P Ar parms
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is equivalent to adding the parameter
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line
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.Em parms
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to the
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.Pa /etc/gateways
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file.
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.El
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.Pp
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Any other argument supplied is interpreted as the name
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of a file in which the actions of
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.Nm
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should be logged.
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It is better to use
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.Fl T
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instead of
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appending the name of the trace file to the command.
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.Pp
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.Nm
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also supports the notion of
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"distant"
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.Em passive
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or
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.Em active
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gateways.
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When
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.Nm
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is started, it reads the file
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.Pa /etc/gateways
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to find such distant gateways which may not be located using
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only information from a routing socket, to discover if some
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of the local gateways are
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.Em passive ,
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and to obtain other parameters.
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Gateways specified in this manner should be marked passive
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if they are not expected to exchange routing information,
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while gateways marked active
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should be willing to exchange RIP packets.
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Routes through
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.Em passive
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gateways are installed in the
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kernel's routing tables once upon startup and are not included in
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transmitted RIP responses.
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.Pp
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Distant active gateways are treated like network interfaces.
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RIP responses are sent
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to the distant
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.Em active
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gateway.
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If no responses are received, the associated route is deleted from
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the kernel table and RIP responses advertised via other interfaces.
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If the distant gateway resumes sending RIP responses, the associated
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route is restored.
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.Pp
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Such gateways can be useful on media that do not support broadcasts
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or multicasts but otherwise act like classic shared media like
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Ethernets such as some ATM networks.
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One can list all RIP routers reachable on the ATM network in
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.Pa /etc/gateways
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with a series of
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"host" lines.
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.Pp
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Gateways marked
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.Em external
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are also passive, but are not placed in the kernel
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routing table nor are they included in routing updates.
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The function of external entries is to indicate
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that another routing process
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will install such a route if ncessary,
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and that alternate routes to that destination should not be installed
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by
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.Nm routed .
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Such entries are only required when both routers may learn of routes
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to the same destination.
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.Pp
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The
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.Em /etc/gateways
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file is comprised of a series of lines, each in
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one of the following formats or consist of parameters described below:
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.Pp
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.Bd -ragged
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.Cm net
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.Ar Nname[/mask]
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.Cm gateway
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.Ar Gname
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.Cm metric
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.Ar value
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.Pf < Cm passive No \&|
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.Cm active No \&|
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.Cm extern Ns >
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.Ed
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.Bd -ragged
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.Cm host
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.Ar Hname
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.Cm gateway
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.Ar Gname
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.Cm metric
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.Ar value
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.Pf < Cm passive No \&|
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.Cm active No \&|
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.Cm extern Ns >
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.Ed
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.Pp
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.Ar Nname
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or
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.Ar Hname
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is the name of the destination network or host.
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It may be a symbolic network name or an Internet address
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specified in "dot" notation (see
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.Xr inet 3 ).
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(If it is a name, then it must either be defined in
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.Pa /etc/networks
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or
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.Pa /etc/hosts ,
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or
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.Xr named 8 ,
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must have been started before
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.Xr routed Ns .)
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.Pp
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.Ar mask
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is an optional number between 1 and 32 indicating the netmask associated
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with
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.Ar Nname .
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.Pp
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.Ar Gname
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is the name or address of the gateway to which RIP responses should
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be forwarded.
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.Pp
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.Ar Value
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is the hop count to the destination host or network.
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.Ar " host hname "
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is equivalent to
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.Ar " net nname/32 ".
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.Pp
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One of the keywords
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.Cm passive ,
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.Cm active
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or
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.Cm external
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must be present to indicate whether the gateway should be treated as
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.Cm passive
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or
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.Cm active
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(as described above),
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or whether the gateway is
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.Cm external
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to the scope of the RIP protocol.
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.Pp
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Lines that start with neither "net" nor "host" must consist of one
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or more of the following parameter settings, separated by commas or
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blanks:
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.Bl -tag -width Ds
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.It Cm if Ns \&= Ns Ar ifname
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indicates that the other parameters on the line apply to the interface
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name
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.Ar ifname .
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.It Cm subnet Ns \&= Ns Ar nname[/mask][,metric]
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advertises a route to network
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.AR nname
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with mask
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.AR mask
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and the supplied metric (default 1).
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This is useful for filling "holes" in CIDR allocations.
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This parameter must appear by itself on a line.
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.Pp
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Do not use this feature unless necessary. It is dangerous.
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.It Cm passwd Ns \&= Ns Ar XXX
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specifies a RIPv2 password that will be included on all RIPv2
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responses sent and checked on all RIPv2 responses received.
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The password must not contain any blanks, tab characters, commas
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or '#' characters.
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.It Cm no_ag
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turns off aggregation of subnets in RIPv1 and RIPv2 responses.
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.It Cm no_super_ag
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turns off aggregation of networks into supernets in RIPv2 responses.
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.It Cm passive
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is equivalent
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.Cm no_rip Cm no_rdisc .
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.It Cm no_rip
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disables all RIP processing on the specified interface.
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If no interfaces are allowed to process RIP packets,
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.Nm
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acts purely as a router discovery daemon.
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.Cm No_rip
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is equivalent to
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.Cm no_ripv1_in no_ripv2_in no_ripv1_out no_ripv2_out .
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Note that turning off RIP without explicitly turning on router
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discovery advertisements with
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.Cm rdisc_adv
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or
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.Fl s
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causes
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.Nm routed
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to act as a client router discovery daemon, not adveritising.
|
|
.It Cm no_ripv1_in
|
|
causes RIPv1 received responses to be ignored.
|
|
.It Cm no_ripv2_in
|
|
causes RIPv2 received responses to be ignored.
|
|
.It Cm ripv2_out
|
|
turns off RIPv1 output and causes RIPv2 advertisements to be
|
|
multicast when possible.
|
|
.It Cm no_rdisc
|
|
disables the Internet Router Discovery Protocol.
|
|
.It Cm no_solicit
|
|
disables the tranmission of Router Discovery Solicitations.
|
|
.It Cm send_solicit
|
|
specifies that Router Discovery solicitations should be sent,
|
|
even on point-to-point links,
|
|
which by default only listen to Router Discovery messages.
|
|
.It Cm no_rdisc_adv
|
|
disables the transmission of Router Discovery Advertisements
|
|
.It Cm rdisc_adv
|
|
specifies that Router Discovery advertisements should be sent,
|
|
even on point-to-point links,
|
|
which by default only listen to Router Discovery messages
|
|
.It Cm bcast_rdisc
|
|
specifies that Router Discovery packets should be broadcast instead of
|
|
multicast.
|
|
.It Cm rdisc_pref Ns \&= Ns Ar N
|
|
sets the preference in Router Discovery Advertisements to the integer
|
|
.Ar N .
|
|
.It Cm rdisc_interval Ns \&= Ns Ar N
|
|
sets the nominal interval with which Router Discovery Advertisements
|
|
are transmitted to N seconds and their lifetime to 3*N.
|
|
.It Cm fake_default Ns \&= Ns Ar metric
|
|
has an identical effect to
|
|
.Fl F Ar net[/mask][,metric]
|
|
with the network and mask coming from the sepcified interface.
|
|
.It Cm pm_rdisc
|
|
is similar to
|
|
.Cm 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
|
|
.Cm fake_default ,
|
|
the default route is broadcast with a metric of 14.
|
|
That serves as a "poor man's router discovery" protocol.
|
|
.El
|
|
.Pp
|
|
Note that the netmask associated with point-to-point links (such as SLIP
|
|
or PPP, with the IFF_POINTOPOINT flag) is used by
|
|
.Nm routed
|
|
to infer the netmask used by the remote system when RIPv1 is used.
|
|
.Pp
|
|
.Sh FILES
|
|
.Bl -tag -width /etc/gateways -compact
|
|
.It Pa /etc/gateways
|
|
for distant gateways
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr gated 8 ,
|
|
.Xr udp 4 ,
|
|
.Xr icmp 4 ,
|
|
.Xr htable 8 ,
|
|
.Xr rtquery 8 .
|
|
.Rs
|
|
.%T Internet Transport Protocols
|
|
.%R XSIS 028112
|
|
.%Q Xerox System Integration Standard
|
|
.Re
|
|
.Sh BUGS
|
|
It does not always detect unidirectional failures in network interfaces
|
|
(e.g., when the output side fails).
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
command appeared in
|
|
.Bx 4.2 .
|