Sun Microsystems Sun Workstation 100U System Manager's Manual page 240

ROUTED(8C)
MAINTENANCE COMMANDS
ROUTED (8C)
NAME
routed - network routing daemon
SYNOPSIS
/u8r /ete/tn.routed ( _ ] [ -q] [ -t ] [
logfile]
DESCRIPTION
R outed is invoked at boot time to manage the network routing tables. The routing daemon uses
3 ,
variant of the Xerox NS Routing Information Protocol in maintaining up to date kernel routing
table entries.
In normal operation routed listens on udp(4P) socket 520
(decimal) for routing information pack-
ets. 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 ioetl to find those directly connected inter-
faces 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 broadcast packet if the inter-
(ace supports it) and enters a loop, listening (or request and response packets from other hosts.
When a request packet is received, routed (ormulates 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 o( 16, or greater, is considered "infinite"). The
metric associated with each route returned provides a metric relative to the sender.
R~que8t
packets received by routed are used to update the routing tables if one oC the following
co~ditions
is satisfied:
(1)
(2)
(3)
(4)
No routing table entry exists (or the destination network or host, and the metric indicates
the destination is "reachable" (that is, the hop count is not infinite).
The source host of the packet is the same as the router in the existing routing table
entry. That is, updated inCormation is being received from the very internetwork router
through which packets for the destination are being routed.
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.
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.
W~en
an update is applied, routed records the change in its internal tables and generates a
re8ponBe packet to all directly connected hosts and networks. Routed waits a short period
oC 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 (or 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 gra.tuitously supply their routing tables every
30
seconds to
all directly connected hosts and networks.
Supplying the
.-8
option forces routed to supply routing inCormation whether it is acting as an
internetwork router or not. The -q
option is the opposite o( the _ 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 (rom 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 a
SUD
Release 1.1
Last change: 28 October 1983
85