# 2.11BSD#431 - /usr/man/cat8/routed.0

    ROUTED(8)	    UNIX Programmer's Manual		ROUTED(8)

    NAME
         routed - network routing daemon

    SYNOPSIS
         routed [ -d ] [ -g ] [ -s ] [ -q ] [ -t ] [ logfile ]

    DESCRIPTION
         Routed is invoked at boot time to manage the network routing
         tables.  The routing daemon uses a variant of the Xerox NS
         Routing Information Protocol in maintaining up to date ker-
         nel routing table entries.  It used a generalized protocol
         capable of use with multiple address types, but is currently
         used only for Internet routing within a cluster of networks.

         In normal operation routed listens on the udp(4) socket for
         the route service (see services(5)) for routing information
         packets.  If the host is an internetwork router, it periodi-
         cally supplies copies of its routing tables to any directly
         connected hosts and networks.

         When routed is started, it uses the SIOCGIFCONF ioctl to
         find those directly connected interfaces configured into the
         system and marked ``up'' (the software loopback interface is
         ignored).	If multiple interfaces are present, it is assumed
         that the host will forward packets between networks.  Routed
         then transmits a request packet on each interface (using a
         broadcast packet if the interface supports it) and enters a
         loop, listening for request and response packets from other
         hosts.

         When a request packet is received, routed formulates a reply
         based on the information maintained in its internal tables.
         The response packet generated contains a list of known
         routes, each marked with a ``hop count'' metric (a count of
         16, or greater, is considered ``infinite'').  The metric
         associated with each route returned provides a metric rela-
         tive to the sender.

         Response packets received by routed are used to update the
         routing tables if one of the following conditions is satis-
         fied:

         (1)  No routing table entry exists for the destination net-
    	  work or host, and the metric indicates the destination
    	  is ``reachable'' (i.e. the hop count is not infinite).

         (2)  The source host of the packet is the same as the router
    	  in the existing routing table entry.	That is, updated
    	  information is being received from the very internet-
    	  work router through which packets for the destination
    	  are being routed.

    Printed 11/26/99	November 17, 1996			1

    ROUTED(8)	    UNIX Programmer's Manual		ROUTED(8)

         (3)  The existing entry in the routing table has not been
    	  updated for some time (defined to be 90 seconds) and
    	  the route is at least as cost effective as the current
    	  route.

         (4)  The new route describes a shorter route to the destina-
    	  tion than the one currently stored in the routing
    	  tables; the metric of the new route is compared against
    	  the one stored in the table to decide this.

         When an update is applied, routed records the change in its
         internal tables and updates the kernel routing table.  The
         change is reflected in the next response packet sent.

         In addition to processing incoming packets, routed also
         periodically checks the routing table entries.  If an entry
         has not been updated for 3 minutes, the entry's metric is
         set to infinity and marked for deletion.  Deletions are
         delayed an additional 60 seconds to insure the invalidation
         is propagated throughout the local internet.

         Hosts acting as internetwork routers gratuitously supply
         their routing tables every 30 seconds to all directly con-
         nected hosts and networks.  The response is sent to the
         broadcast address on nets capable of that function, to the
         destination address on point-to-point links, and to the
         router's own address on other networks.  The normal routing
         tables are bypassed when sending gratuitous responses.  The
         reception of responses on each network is used to determine
         that the network and interface are functioning correctly.
         If no response is received on an interface, another route
         may be chosen to route around the interface, or the route
         may be dropped if no alternative is available.

         Routed supports several options:

         -d   Enable additional debugging information to be logged,
    	  such as bad packets received.

         -g   This flag is used on internetwork routers to offer a
    	  route to the ``default'' destination.  This is typi-
    	  cally used on a gateway to the Internet, or on a gate-
    	  way that uses another routing protocol whose routes are
    	  not reported to other local routers.

         -s   Supplying this option forces routed to supply routing
    	  information whether it is acting as an internetwork
    	  router or not.  This is the default if multiple network
    	  interfaces are present, or if a point-to-point link is
    	  in use.

         -q   This is the opposite of the -s option.

    Printed 11/26/99	November 17, 1996			2

    ROUTED(8)	    UNIX Programmer's Manual		ROUTED(8)

         -t   If the -t option is specified, all packets sent or
    	  received are printed on the standard output.	In addi-
    	  tion, routed will not divorce itself from the control-
    	  ling terminal so that interrupts from the keyboard will
    	  kill the process.

         Any other argument supplied is interpreted as the name of
         file in which routed's actions should be logged.  This log
         contains information about any changes to the routing tables
         and, if not tracing all packets, a history of recent mes-
         sages sent and received which are related to the changed
         route.

         In addition to the facilities described above, routed sup-
         ports the notion of ``distant'' passive and active gateways.
         When routed is started up, it reads the file /etc/gateways
         to find gateways which may not be located using only infor-
         mation from the SIOGIFCONF ioctl.	Gateways specified in
         this manner should be marked passive if they are not
         expected to exchange routing information, while gateways
         marked active should be willing to exchange routing informa-
         tion (i.e.  they should have a routed process running on the
         machine).	Passive gateways are maintained in the routing
         tables forever and information regarding their existence is
         included in any routing information transmitted.  Active
         gateways are treated equally to network interfaces.  Routing
         information is distributed to the gateway and if no routing
         information is received for a period of the time, the asso-
         ciated route is deleted.  External gateways are also pas-
         sive, but are not placed in the kernel routing table nor are
         they included in routing updates.	The function of external
         entries is to inform routed that another routing process
         will install such a route, and that alternate routes to that
         destination should not be installed.  Such entries are only
         required when both routers may learn of routes to the same
         destination.

         The /etc/gateways is comprised of a series of lines, each in
         the following format:

         < net | host > name1 gateway name2 metric value < passive | active | external >

         The net or host keyword indicates if the route is to a net-
         work or specific host.

         Name1 is the name of the destination network or host.  This
         may be a symbolic name located in /etc/networks or
         /etc/hosts (or, if started after named(8), known to the name
         server), or an Internet address specified in ``dot'' nota-
         tion; see inet(3).

    Printed 11/26/99	November 17, 1996			3

    ROUTED(8)	    UNIX Programmer's Manual		ROUTED(8)

         Name2 is the name or address of the gateway to which mes-
         sages should be forwarded.

         Value is a metric indicating the hop count to the destina-
         tion host or network.

         One of the keywords passive, active or external indicates if
         the gateway should be treated as passive or active (as
         described above), or whether the gateway is external to the
         scope of the routed protocol.

         Internetwork routers that are directly attached to the
         Arpanet or Milnet should use the Exterior Gateway Protocol
         (EGP) to gather routing information rather then using a
         static routing table of passive gateways.	EGP is required
         in order to provide routes for local networks to the rest of
         the Internet system.  Sites needing assistance with such
         configurations should contact the Computer Systems Research
         Group at Berkeley.

    FILES
         /etc/gateways  for distant gateways

    SEE ALSO
         ``Internet Transport Protocols'', XSIS 028112, Xerox System
         Integration Standard.
         udp(4), XNSrouted(8), htable(8)

    BUGS
         The kernel's routing tables may not correspond to those of
         routed when redirects change or add routes.  The only remedy
         for this is to place the routing process in the kernel.

         Routed should incorporate other routing protocols, such as
         Xerox NS (XNSrouted(8)) and EGP.  Using separate processes
         for each requires configuration options to avoid redundant
         or competing routes.

         Routed should listen to intelligent interfaces, such as an
         IMP, and to error protocols, such as ICMP, to gather more
         information.  It does not always detect unidirectional
         failures in network interfaces (e.g., when the output side
         fails).

    Printed 11/26/99	November 17, 1996			4

Generated: 2016-12-26 | Generated by man2html V0.25 page hit count: 710 |