routed(8c)																routed(8c)

Name
       routed - network routing daemon

Syntax
       /etc/routed [ options ] [ logfile ]

Description
       The program is invoked at boot time to manage the network routing tables.  The routing daemon uses a variant of the Xerox NS Routing Infor-
       mation Protocol in maintaining up-to-date kernel routing table entries.

       In normal operation the program listens on a socket for packets of routing information.	If the host is an internetwork router, it periodi-
       cally supplies copies of its routing tables to any directly connected hosts and networks.

       When  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 net-
       works.	The command 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, formulates a reply based on the information maintained in its internal tables.  The response packet gen-
       erated  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 "relative to the sender".

       The response packets received by are used to update the routing tables if one of the following conditions is satisfied:

       o   No routing table entry exists for the destination network or host, and the metric indicates the destination is reachable.  That is, the
	   hop count is not infinite.

       o   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 internetwork router through which packets for the destination are being routed.

       o   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.

       o   The	new  route describes a shorter route to the destination 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, the command records the change in its internal tables and generates a response packet to all directly  connected
       hosts  and  networks.   The  command waits a short period of time (no more than 30 seconds) before modifying the kernel's routing tables to
       allow possible unstable situations to settle.

       In addition to processing incoming packets, the command 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 internet.

       Hosts acting as internetwork routers supply their routing tables every 30 seconds to  all  directly  connected  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 responses.	The reception of responses on each
       network	is used to determine if that 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.

       The program supports the notion of distant passive and active gateways.	When is started up, it reads the file to find gateways	which  may
       not  be	identified  using  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 information (that is, they should  have  a
       process running on the machine).  Passive gateways are maintained indefinitely in routing tables.  Note, however, that passive gateways are
       known only to the local host that lists them in its file.  Information about passive gateways is not included in  any  routing  information
       that is 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 time, the associated route is deleted.

       External gateways are also passive, but are not placed in the kernel routing table nor are they included in routing updates.  The  function
       of  external  entries  is  to  inform 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 is 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 network or specific host.

       The name1 is the name of the destination network or host.  This may be a symbolic name located in or or an Internet  address  specified	in
       dot notation.  For further information, see

       The name2 is the name or address of the gateway to which messages should be forwarded.

       The value is a metric indicating the hop count to the destination host or network.

       The  keywords  passive,	active,  or  external indicate if the gateway should be treated as passive or active (as previously described), or
       whether the gateway is external to the scope of the protocol.

       Any other argument supplied is interpreted as the name of a file in which the actions of should be logged.  This log  contains  information
       about any changes to the routing tables and a history of recent messages sent and received which are related to the changed route.

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

       -g   Offers  a  route,  on  internetwork routers, to the default destination.  This is typically used on a gateway to the Internet, or on a
	    gateway that uses another routing protocol whose routes are not reported to other local routers.

       -s   Forces to supply routing information whether it is acting as an internetwork router or not.

       -q   Opposite of the option.

       -t   Prints all packets, sent or received, on the standard output.  In addition, continues to receive input from the controlling  terminal,
	    so that interrupts from the keyboard will kill the process.

Restrictions
       The  kernel's  routing  tables may not correspond to those of for short periods of time while processes utilizing existing routes exit; the
       only remedy for this is to place the routing process in the kernel.

       The command should listen to intelligent interfaces, such as an IMP, and to error protocols, such as  ICMP,  to	gather	more  information.
       However, it does not always detect unidirectional failures in network interfaces, such as when the output side fails.

Files
       For distant gateways

See Also
       udp(4p), htable(8)

																	routed(8c)