360 lines
11 KiB
Groff
360 lines
11 KiB
Groff
.\" 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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.\" from: @(#)routed.8 8.2 (Berkeley) 12/11/93
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.\" $Id: routed.8,v 1.5 1994/05/13 08:04:48 mycroft Exp $
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.\"
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.Dd December 11, 1993
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.Dt ROUTED 8
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.Os BSD 4.2
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.Sh NAME
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.Nm routed
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.Nd network routing daemon
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.Sh SYNOPSIS
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.Nm routed
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.Op Fl d
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.Op Fl g
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.Op Fl q
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.Op Fl s
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.Op Fl t
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.Op Ar logfile
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.Sh DESCRIPTION
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.Nm Routed
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is invoked at boot time to manage the network routing tables.
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The routing daemon uses a variant of the Xerox NS Routing
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Information Protocol in maintaining up to date kernel routing
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table entries.
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It used a generalized protocol capable of use with multiple
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address types, but is currently used only for Internet routing
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within a cluster of networks.
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.Pp
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In normal operation
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.Nm routed
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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 packets. If the host is an
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internetwork router, it periodically supplies copies
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of its routing tables to any directly connected hosts
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and networks.
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.Pp
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When
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.Nm routed
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is started, it uses the
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.Dv SIOCGIFCONF
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.Xr ioctl 2
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to find those
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directly connected interfaces configured into the
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system and marked ``up'' (the software loopback interface
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is ignored). If multiple interfaces
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are present, it is assumed that the host will forward packets
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between networks.
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.Nm Routed
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then transmits a
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.Em request
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packet on each interface (using a broadcast packet if
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the interface supports it) and enters a loop, listening
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for
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.Em request
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and
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.Em response
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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 routed
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formulates a reply based on the information maintained in its
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internal tables. 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''). The metric associated with each
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route returned provides a metric
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.Em relative to the sender .
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.Pp
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.Em Response
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packets received by
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.Nm routed
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are used to update the routing tables if one of the following
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conditions is satisfied:
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.Bl -enum
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.It
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No routing table entry exists for the destination network
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or host, and the metric indicates the destination is ``reachable''
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(i.e. the hop count is not infinite).
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.It
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The source host of the packet is the same as the router in the
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existing routing table entry. That is, updated information is
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being received from the very internetwork router through which
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packets for the destination are being routed.
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.It
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The existing entry in the routing table has not been updated for
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some time (defined to be 90 seconds) and the route is at least
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as cost effective as the current route.
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.It
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The new route describes a shorter route to the destination than
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the one currently stored in the routing tables; the metric of
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the new route is compared against the one stored in the table
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to decide this.
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.El
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.Pp
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When an update is applied,
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.Nm routed
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records the change in its internal tables and updates the kernel
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routing table.
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The change is reflected in the next
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.Em response
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packet sent.
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.Pp
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In addition to processing incoming packets,
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.Nm routed
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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. Deletions are delayed
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an additional 60 seconds to insure the invalidation is propagated
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throughout the local internet.
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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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The response is sent to the broadcast address on nets capable of that function,
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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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The normal routing tables are bypassed when sending gratuitous responses.
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The reception of responses on each network is used to determine that the
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network and interface are functioning correctly.
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If no response is received on an interface, another route may be chosen
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to route around the interface, or the route may be dropped if no alternative
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is available.
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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 d
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Enable additional debugging information to be logged,
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such as bad packets received.
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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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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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.It Fl s
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Supplying this
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option forces
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.Nm routed
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to supply routing information whether it is acting as an internetwork
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router or not.
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This is the default if multiple network interfaces are present,
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or if a point-to-point link is in use.
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.It Fl q
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This
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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 t
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If the
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.Fl t
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option is specified, all packets sent or received are
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printed on the standard output. In addition,
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.Nm routed
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will not divorce itself from the controlling terminal
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so that interrupts from the keyboard will kill the process.
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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 file in which
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.Nm routed Ns \'s
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actions should be logged. This log contains information
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about any changes to the routing tables and, if not tracing all packets,
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a history of recent messages sent and received which are related to
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the changed route.
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.Pp
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In addition to the facilities described above,
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.Nm routed
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supports the notion of ``distant''
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.Em passive
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and
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.Em active
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gateways. When
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.Nm routed
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is started up, it reads the file
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.Pa /etc/gateways
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to find gateways which may not be located using
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only information from the
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.Dv SIOGIFCONF
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.Xr ioctl 2 .
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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 routing information (i.e.
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they should have a
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.Nm routed
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process running on the machine).
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Routes through passive gateways are installed in the
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kernel's routing tables once upon startup.
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Such routes are not included in
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any routing information transmitted.
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Active gateways are treated equally to network
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interfaces. Routing information is distributed
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to the gateway and if no routing information is
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received for a period of time, the associated
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route is deleted.
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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 inform
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.Nm routed
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that another routing process
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will install such a route, and that alternate routes to that destination
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should not be installed.
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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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.Pa /etc/gateways
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is comprised of a series of lines, each in
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the following format:
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.Bd -ragged
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.Pf < Cm net No \&|
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.Cm host Ns >
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.Ar name1
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.Cm gateway
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.Ar name2
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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 external Ns >
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.Ed
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.Pp
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The
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.Cm net
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or
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.Cm host
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keyword indicates if the route is to a network or specific host.
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.Pp
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.Ar Name1
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is the name of the destination network or host. This may be a
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symbolic name located 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, if started after
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.Xr named 8 ,
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known to the name server),
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or an Internet address specified in ``dot'' notation; see
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.Xr inet 3 .
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.Pp
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.Ar Name2
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is the name or address of the gateway to which messages should
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be forwarded.
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.Pp
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.Ar Value
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is a metric indicating the hop count to the destination host
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or network.
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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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indicates if the gateway should be treated as
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.Em passive
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or
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.Em active
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(as described above),
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or whether the gateway is
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.Em external
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to the scope of the
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.Nm routed
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protocol.
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.Pp
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Internetwork routers that are directly attached to the Arpanet or Milnet
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should use the Exterior Gateway Protocol
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.Pq Tn EGP
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to gather routing information
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rather then using a static routing table of passive gateways.
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.Tn EGP
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is required in order to provide routes for local networks to the rest
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of the Internet system.
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.Sh FILES
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.Bl -tag -width /etc/gateways -compact
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.It Pa /etc/gateways
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for distant gateways
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.El
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.Sh SEE ALSO
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.Xr udp 4 ,
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.Xr icmp 4 ,
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.Xr XNSrouted 8 ,
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.Xr htable 8
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.Rs
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.%T Internet Transport Protocols
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.%R XSIS 028112
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.%Q Xerox System Integration Standard
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.Re
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.Sh BUGS
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The kernel's routing tables may not correspond to those of
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.Nm routed
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when redirects change or add routes.
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.Nm Routed
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should note any redirects received by reading
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the
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.Tn ICMP
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packets received via a raw socket.
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.Pp
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.Nm Routed
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should incorporate other routing protocols,
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such as Xerox
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.Tn \&NS
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.Pq Xr XNSrouted 8
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and
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.Tn EGP .
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Using separate processes for each requires configuration options
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to avoid redundant or competing routes.
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.Pp
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.Nm Routed
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should listen to intelligent interfaces, such as an
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.Tn IMP ,
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to gather more information.
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It does not always detect unidirectional failures in network interfaces
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(e.g., when the output side fails).
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.Sh HISTORY
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The
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.Nm
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command appeared in
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.Bx 4.2 .
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