.TH ROUTED 8 "3 February 1983"
routed \- network routing daemon
is invoked at boot time to manage the network routing tables.
The routing daemon utilizes a variant of the Xerox NS Routing
Information Protocol in maintaining up to date kernel routing
for routing information packets. If the host is an
internetwork router, it periodically supplies copies
of its routing tables to any directly connected hosts
is started, it reads from
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
packet on each interface (using a broadcast packet if
the interface supports it) and enters a loop, listening
packets from other hosts.
formulates a reply based on the information maintained in its
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
.IR "relative to the sender" .
are used to update the routing tables if one of the following
No routing table entry exists for the destination network
or host, and the metric indicates the destination is ``reachable''
(i.e. 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 information 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
When an update is applied,
records the change in its internal tables and generates a
packet to all directly connected hosts and networks.
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,
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
Hosts acting as internetwork routers gratuitously supply their
routing tables every 30 seconds to all directly connected hosts
to supply routing information whether it is acting as an internetwork
option is the opposite of the
option is specified, all packets sent or received are
printed on the standard output. In addition,
will not divorce itself from the controlling terminal
so that interrupts from the keyboard will kill the process.
/dev/kmem to find the network interfaces,
/etc/gateways to find connected gateways not running a version of
"Internet Transport Protocols", XSIS 028112, Xerox System Integration
"4.2BSD Routing Protocol", by Sam Leffler.
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
should listen to intelligent interfaces, such as an IMP, and
to error protocols, such as ICMP, to gather more information.