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Annotation of 43BSDTahoe/man/man8/routed.8, revision 1.1

1.1     ! root        1: .\" Copyright (c) 1983 Regents of the University of California.
        !             2: .\" All rights reserved.  The Berkeley software License Agreement
        !             3: .\" specifies the terms and conditions for redistribution.
        !             4: .\"
        !             5: .\"    @(#)routed.8c   6.3 (Berkeley) 2/10/87
        !             6: .\"
        !             7: .TH ROUTED 8C "February 10, 1987"
        !             8: .UC 5
        !             9: .SH NAME
        !            10: routed \- network routing daemon
        !            11: .SH SYNOPSIS
        !            12: .B /etc/routed
        !            13: [
        !            14: .B \-d
        !            15: ] [
        !            16: .B \-g
        !            17: ] [
        !            18: .B \-s
        !            19: ] [
        !            20: .B \-q
        !            21: ] [
        !            22: .B \-t
        !            23: ] [
        !            24: .I logfile
        !            25: ]
        !            26: .SH DESCRIPTION
        !            27: .I Routed
        !            28: is invoked at boot time to manage the network routing tables.
        !            29: The routing daemon uses a variant of the Xerox NS Routing
        !            30: Information Protocol in maintaining up to date kernel routing
        !            31: table entries.
        !            32: It used a generalized protocol capable of use with multiple
        !            33: address types, but is currently used only for Internet routing
        !            34: within a cluster of networks.
        !            35: .PP
        !            36: In normal operation
        !            37: .I routed
        !            38: listens on the
        !            39: .IR udp (4P)
        !            40: socket for the
        !            41: .I route
        !            42: service (see
        !            43: .IR services (5))
        !            44: for routing information packets.  If the host is an
        !            45: internetwork router, it periodically supplies copies
        !            46: of its routing tables to any directly connected hosts
        !            47: and networks.
        !            48: .PP
        !            49: When
        !            50: .I routed
        !            51: is started, it uses the SIOCGIFCONF
        !            52: .I ioctl
        !            53: to find those
        !            54: directly connected interfaces configured into the
        !            55: system and marked ``up'' (the software loopback interface
        !            56: is ignored).  If multiple interfaces
        !            57: are present, it is assumed that the host will forward packets
        !            58: between networks.
        !            59: .I Routed
        !            60: then transmits a 
        !            61: .I request
        !            62: packet on each interface (using a broadcast packet if
        !            63: the interface supports it) and enters a loop, listening
        !            64: for
        !            65: .I request
        !            66: and
        !            67: .I response
        !            68: packets from other hosts.
        !            69: .PP
        !            70: When a
        !            71: .I request
        !            72: packet is received, 
        !            73: .I routed
        !            74: formulates a reply based on the information maintained in its
        !            75: internal tables.  The
        !            76: .I response
        !            77: packet generated contains a list of known routes, each marked
        !            78: with a ``hop count'' metric (a count of 16, or greater, is
        !            79: considered ``infinite'').  The metric associated with each
        !            80: route returned provides a metric
        !            81: .IR "relative to the sender" .
        !            82: .PP
        !            83: .I Response
        !            84: packets received by
        !            85: .I routed
        !            86: are used to update the routing tables if one of the following
        !            87: conditions is satisfied:
        !            88: .TP
        !            89: (1)
        !            90: No routing table entry exists for the destination network
        !            91: or host, and the metric indicates the destination is ``reachable''
        !            92: (i.e. the hop count is not infinite).
        !            93: .TP
        !            94: (2)
        !            95: The source host of the packet is the same as the router in the
        !            96: existing routing table entry.  That is, updated information is
        !            97: being received from the very internetwork router through which
        !            98: packets for the destination are being routed.
        !            99: .TP
        !           100: (3)
        !           101: The existing entry in the routing table has not been updated for
        !           102: some time (defined to be 90 seconds) and the route is at least
        !           103: as cost effective as the current route.
        !           104: .TP
        !           105: (4)
        !           106: The new route describes a shorter route to the destination than
        !           107: the one currently stored in the routing tables; the metric of
        !           108: the new route is compared against the one stored in the table
        !           109: to decide this.
        !           110: .PP
        !           111: When an update is applied,
        !           112: .I routed
        !           113: records the change in its internal tables and updates the kernel
        !           114: routing table.
        !           115: The change is reflected in the next
        !           116: .I response
        !           117: packet sent.
        !           118: .PP
        !           119: In addition to processing incoming packets,
        !           120: .I routed
        !           121: also periodically checks the routing table entries.
        !           122: If an entry has not been updated for 3 minutes, the entry's metric
        !           123: is set to infinity and marked for deletion.  Deletions are delayed
        !           124: an additional 60 seconds to insure the invalidation is propagated
        !           125: throughout the local internet.
        !           126: .PP
        !           127: Hosts acting as internetwork routers gratuitously supply their
        !           128: routing tables every 30 seconds to all directly connected hosts
        !           129: and networks.
        !           130: The response is sent to the broadcast address on nets capable of that function,
        !           131: to the destination address on point-to-point links, and to the router's
        !           132: own address on other networks.
        !           133: The normal routing tables are bypassed when sending gratuitous responses.
        !           134: The reception of responses on each network is used to determine that the
        !           135: network and interface are functioning correctly.
        !           136: If no response is received on an interface, another route may be chosen
        !           137: to route around the interface, or the route may be dropped if no alternative
        !           138: is available.
        !           139: .PP
        !           140: .I Routed supports several options:
        !           141: .TP
        !           142: .B \-d
        !           143: Enable additional debugging information to be logged,
        !           144: such as bad packets received.
        !           145: .TP
        !           146: .B \-g
        !           147: This flag is used on internetwork routers to offer a route
        !           148: to the ``default'' destination.
        !           149: This is typically used on a gateway to the Internet,
        !           150: or on a gateway that uses another routing protocol whose routes
        !           151: are not reported to other local routers.
        !           152: .TP
        !           153: .B \-s
        !           154: Supplying this
        !           155: option forces 
        !           156: .I routed
        !           157: to supply routing information whether it is acting as an internetwork
        !           158: router or not.
        !           159: This is the default if multiple network interfaces are present,
        !           160: or if a point-to-point link is in use.
        !           161: .TP
        !           162: .B \-q
        !           163: This
        !           164: is the opposite of the
        !           165: .B \-s
        !           166: option.
        !           167: .TP
        !           168: .B \-t
        !           169: If the
        !           170: .B \-t
        !           171: option is specified, all packets sent or received are
        !           172: printed on the standard output.  In addition,
        !           173: .I routed
        !           174: will not divorce itself from the controlling terminal
        !           175: so that interrupts from the keyboard will kill the process.
        !           176: .PP
        !           177: Any other argument supplied is interpreted as the name
        !           178: of file in which 
        !           179: .IR routed 's
        !           180: actions should be logged.  This log contains information
        !           181: about any changes to the routing tables and, if not tracing all packets,
        !           182: a history of recent messages sent and received which are related to
        !           183: the changed route.
        !           184: .PP
        !           185: In addition to the facilities described above, 
        !           186: .I routed
        !           187: supports the notion of ``distant''
        !           188: .I passive
        !           189: and 
        !           190: .I active
        !           191: gateways.  When 
        !           192: .I routed
        !           193: is started up, it reads the file
        !           194: .I /etc/gateways
        !           195: to find gateways which may not be located using
        !           196: only information from the SIOGIFCONF
        !           197: .IR ioctl .
        !           198: Gateways specified in this manner should be marked passive
        !           199: if they are not expected to exchange routing information,
        !           200: while gateways marked active
        !           201: should be willing to exchange routing information (i.e.
        !           202: they should have a
        !           203: .I routed
        !           204: process running on the machine).
        !           205: Routes through passive gateways are installed in the
        !           206: kernel's routing tables once upon startup.
        !           207: Such routes are not included in
        !           208: any routing information transmitted.
        !           209: Active gateways are treated equally to network
        !           210: interfaces.  Routing information is distributed
        !           211: to the gateway and if no routing information is
        !           212: received for a period of the time, the associated
        !           213: route is deleted.
        !           214: Gateways marked
        !           215: .I external
        !           216: are also passive, but are not placed in the kernel
        !           217: routing table nor are they included in routing updates.
        !           218: The function of external entries is to inform
        !           219: .I routed
        !           220: that another routing process
        !           221: will install such a route, and that alternate routes to that destination
        !           222: should not be installed.
        !           223: Such entries are only required when both routers may learn of routes
        !           224: to the same destination.
        !           225: .PP
        !           226: The 
        !           227: .I /etc/gateways
        !           228: is comprised of a series of lines, each in
        !           229: the following format:
        !           230: .PP
        !           231: .nf
        !           232: < \fBnet\fP | \fBhost\fP > \fIname1\fP \fBgateway\fP \fIname2\fP \fBmetric\fP \fIvalue\fP < \fBpassive\fP | \fBactive\fP | \fBexternal\fP >
        !           233: .fi
        !           234: .PP
        !           235: The 
        !           236: .B net
        !           237: or
        !           238: .B host
        !           239: keyword indicates if the route is to a network or specific host.
        !           240: .PP
        !           241: .I Name1
        !           242: is the name of the destination network or host.  This may be a
        !           243: symbolic name located in
        !           244: .I /etc/networks
        !           245: or
        !           246: .I /etc/hosts
        !           247: (or, if started after
        !           248: .IR named (8),
        !           249: known to the name server), 
        !           250: or an Internet address specified in ``dot'' notation; see
        !           251: .IR inet (3N).
        !           252: .PP
        !           253: .I Name2
        !           254: is the name or address of the gateway to which messages should
        !           255: be forwarded.
        !           256: .PP
        !           257: .I Value
        !           258: is a metric indicating the hop count to the destination host
        !           259: or network.
        !           260: .PP
        !           261: One of the keywords
        !           262: .BR passive ,
        !           263: .B active
        !           264: or
        !           265: .B external
        !           266: indicates if the gateway should be treated as 
        !           267: .I passive
        !           268: or
        !           269: .I active
        !           270: (as described above),
        !           271: or whether the gateway is
        !           272: .I external
        !           273: to the scope of the
        !           274: .I routed
        !           275: protocol.
        !           276: .PP
        !           277: Internetwork routers that are directly attached to the Arpanet or Milnet
        !           278: should use the Exterior Gateway Protocol (EGP) to gather routing information
        !           279: rather then using a static routing table of passive gateways.
        !           280: EGP is required in order to provide routes for local networks to the rest
        !           281: of the Internet system.
        !           282: Sites needing assistance with such configurations
        !           283: should contact the Computer Systems Research Group at Berkeley.
        !           284: .SH FILES
        !           285: .DT
        !           286: /etc/gateways  for distant gateways
        !           287: .SH "SEE ALSO"
        !           288: ``Internet Transport Protocols'', XSIS 028112, Xerox System Integration
        !           289: Standard.
        !           290: .br
        !           291: udp(4P), icmp(4P), XNSrouted(8C), htable(8)
        !           292: .SH BUGS
        !           293: The kernel's routing tables may not correspond to those of
        !           294: .I routed
        !           295: when redirects change or add routes.
        !           296: .I Routed
        !           297: should note any redirects received by reading
        !           298: the ICMP packets received via a raw socket.
        !           299: .PP
        !           300: .I Routed
        !           301: should incorporate other routing protocols,
        !           302: such as Xerox NS
        !           303: .RI ( XNSrouted (8C))
        !           304: and EGP.
        !           305: Using separate processes for each requires configuration options
        !           306: to avoid redundant or competing routes.
        !           307: .PP
        !           308: .I Routed
        !           309: should listen to intelligent interfaces, such as an IMP,
        !           310: to gather more information.
        !           311: It does not always detect unidirectional failures in network interfaces
        !           312: (e.g., when the output side fails).

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