routed(1M) DG/UX R4.11MU05 routed(1M)
NAME
routed - network routing server
SYNOPSIS
/usr/bin/routed [ -d ] [ -g ] [ -s ] [ -q ] [ -t ] [ logfile ]
DESCRIPTION
Invoke the routed server (daemon) to manage the network routing
tables. The routing server uses a variant of the Xerox NS Routing
Information Protocol in maintaining up to date kernel routing table
entries. It is used as 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(6P) socket for the
route service (see services(4)) 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 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. The routed server 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 relative to the sender.
Response packets received by routed are used to update the routing
tables if one of the following conditions is satisfied:
(1) 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).
(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 internetwork 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 route.
(4) 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, 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 ensure
the invalidation is propagated throughout the local internet.
Hosts acting as internetwork routers gratuitously 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 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.
The routed command 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 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 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.
-t 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 contains
information about any changes to the routing tables and, if not
tracing all packets, a history of recent messages sent and received
which are related to the changed route.
In addition to the facilities described above, routed supports 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 information from the SIOGIFCONF ioctl.
See gateways(4) for details.
NOTE: If you use routed to define routes, you must specify routes in
/etc/gateways, and not in /etc/tcpip.params. Route
definitions specified in /etc/tcpip.params are not used by
routed. Also, if you use routed, do not change or implement
routes with the route(1M) command.
FILES
/etc/gateways
SEE ALSO
gateways(4), udp(6P).
BUGS
The kernel's routing tables may not correspond to those of routed
when redirects change or add routes. The routed server 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 (for example, when the
output side fails).
The routed server should incorporate other routing protocols, such as
Xerox NS and EGP. Using separate processes for each requires
configuration options to avoid redundant or competing routes.
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