routed(1M) MISC. REFERENCE MANUAL PAGES routed(1M)
NAME
routed - network routing daemon
SYNOPSIS
in.routed [ -qstv ] [ 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.
In normal operation routed listens on udp(4P) socket 520
(decimal) for routing information packets. If the host is
an internetwork router, it periodically supplies copies of
its routing tables to any directly connected hosts and net-
works.
When routed is started, it uses the SIOCGIFCONF ioctl(2) 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
the host will forward packets between networks. routed then
transmits a request packet on each interface (using a broad-
cast 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 relative to the
sender.
request 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 (that is, 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.
(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
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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 generates a response packet to all
directly connected hosts and networks. routed 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, 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 internet.
Hosts acting as internetwork routers gratuitously supply
their routing tables every 30 seconds to all directly con-
nected hosts and networks.
Supplying the -s option forces routed to supply routing
information whether it is acting as an internetwork router
or not. The -q option is the opposite of the -s option. If
the -t option is specified, all packets sent or received are
printed on the standard output. In addition, routed will
not divorce itself from the controlling 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 con-
tains information about any changes to the routing tables
and a history of recent messages sent and received which are
related to the changed route. The -v option allows a log-
file to be created showing the changes made to the routing
tables with a timestamp.
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 gateways to
find gateways which may not be identified using the SIOG-
IFCONF 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
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 infor-
mation transmitted. Active gateways are treated equally to
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network interfaces. Routing information is distributed to
the gateway and if no routing information is received for a
period of the time, the associated route is deleted.
The gateways is comprised of a series of lines, each in the
following format:
< net | host > filename1 gateway filename2 metric value
< passive | active >
The net or host keyword indicates if the route is to a net-
work or specific host.
filename1 is the name of the destination network or host.
This may be a symbolic name located in networks or hosts, or
an Internet address specified in dot notation; see inet(3N).
filename2 is the name or address of the gateway to which
messages should be forwarded.
value is a metric indicating the hop count to the destina-
tion host or network.
The keyword passive or active indicates if the gateway
should be treated as passive or active (as described above).
FILES
/etc/gateways for distant gateways
/etc/networks
/etc/hosts
SEE ALSO
ioctl(2), inet(7), udp(7).
NOTES
The kernel's routing tables may not correspond to those of
routed 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.
routed should listen to intelligent interfaces, such as an
IMP, and to error protocols, such as ICMP, to gather more
information.
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