routed - Manages network routing tables
/usr/sbin/routed [-dgt] [-q|-s] [logfile]
Enables additional debugging information, such as bad
packets received, to be logged. The routed daemon remains
under control of the host that started it; therefore, an
interrupt from the controlling host stops the routed process.
Causes the routing daemon to run on a gateway host.
This option is used on internetwork routers to offer a
route to the default destination. Inhibits the routed
daemon from supplying Routing Information Protocol (RIP)
data. The -q option conflicts with the -s option. Do not
use the -q and -s options together. Causes routed to supply
RIP information even if it is not functioning as an
Internet router. The -s option conflicts with the -q
option. Do not use the -s and -q options together.
Causes all packets sent or received to be written to standard
output. The routed daemon remains under control of
the host that started it; therefore, an interrupt from the
controlling host stops the routed process.
The optional logfile operand specifies a log file where
the routed daemon writes information about its actions.
This log contains information about any changes to the
routing tables and a history of recent route change messages
sent and received that are related to changed
routes.
Use the routed daemon to manage the RIP only. Use gated to
manage RIP plus other protocols.
When routed starts, it finds any interfaces to directly
connected hosts and networks that are configured into the
system and marked as up. If multiple interfaces are present,
routed assumes that the local host forwards packets
between networks. The routed daemon transmits an RIP
request packet on each interface (using a broadcast packet
if the interface supports it) and then enters a loop, listening
for RIP routing requests and response packets from
other hosts. In addition, if routed is to supply RIP
information to other hosts, it periodically sends RIP
update packets (containing copies of its routing tables)
to any directly connected hosts and networks.
When routed receives a RIP request packet and can supply
RIP routing information, (the -s option is set), it generates
a reply (response packet) based on the information
maintained in the kernel routing tables. The response
packet contains a list of known routes, each marked with a
hop count metric (the number of host-to-host connections
in the route). The metric for each route is relative to
the sending host. A metric of 16 or greater is considered
to be infinite, or beyond reach.
Updating Routing Tables [Toc] [Back]
If RIP processing is enabled, routed uses information contained
in the RIP response and update packets from other
hosts to update its routing tables. However, routed uses
the information in the RIP routing packet to update the
tables only if at least one of the following conditions
exists: No routing table entry exists for the destination
network or host, and the metric associated with the route
is finite (that is, the metric is less than 16). The
source host of the packet is the router in the existing
routing table entry. The routing table entry is old and
the new information is about a route that is at least as
efficient as the existing route. The new route is shorter
than the one that is currently stored in the routing
tables. (Note that routed determines relative route
length by comparing the new metric with the one stored in
the routing table.)
When routed updates its internal routing tables, it generates
an RIP update packet to all directly connected hosts
and networks. Before updating the kernel routing tables,
routed pauses for a brief period to allow any unstable
conditions to stabilize.
Besides processing incoming RIP packets, routed also
checks the internal routing table entries periodically.
The metric for any entry that has not been updated for 3
minutes is set to infinity and marked for deletion. The
deletion is delayed for 60 seconds so that information
about the invalidated route can be distributed throughout
the network. A host that acts as an RIP router supplies
its routing tables to all directly connected hosts and
networks every 30 seconds.
Using Gateways [Toc] [Back]
In addition to managing routes to directly connected hosts
and networks, routed maintains information about distant
and external gateways. At startup, routed reads the
/etc/gateways file to learn about these gateways.
The /etc/gateways file contains information about routes
through distant and external gateways to hosts and networks
that can be advertised through RIP. These routes are
either static routes to specific destinations, or default
routes that apply when a static route to a destination is
unspecified.
Gateways that supply RIP routing information are marked
active in the /etc/gateways file. The routed daemons distributes
RIP routing information to active gateways; if no
RIP routing information is received from the gateway for a
period of time, routed deletes the associated route from
the routing tables.
Gateways that do not exchange RIP routing information are
marked passive in the /etc/gateways file. The routed daemon
maintains information about passive gateways indefinitely,
and includes information about them in any RIP
routing information transmitted.
Gateways are identified as external to inform routed that
another routing process installs the route.
Information about external gateways is not maintained in
the routing tables. Note that routes through external
gateways must be to networks only.
If a logfile is specified, routed writes information about
its actions to the specified log file. The log contains
information about any changes to the routing tables and a
history of recent route change messages sent and received
that are related to changed routes.
Signals [Toc] [Back]
The following signals have the specified effect when sent
to the routed process using the kill(1) command: Displays
internal routing tables. Broadcasts RIP packets with hop
counts set to infinity. Essentially, these signals disable
the local host as a router. On a second SIGHUP, SIGTERM,
or SIGQUIT, routed terminates.
The gated and routed daemons should not both be run on the
same host, as this may produce unpredictable results.
Routes through external gateways must be to networks only.
Specifies the command path Routes through distant and
external gateways Contains the network name database
Commands: route(8)
Daemons: gated(8)
routed(8)
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