routed(1M) routed(1M)
NAME
routed - network routing daemon
SYNOPSIS
/etc/routed [-s] [-q] [-t] [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 to maintain up-to-date kernel
routing table entries.
In normal operation routed listens on udp(5P) socket 520
(decimal) for routing information packets. If the host is an
inter-network router, it periodically supplies copies of its
routing tables to any directly connected hosts and networks.
When routed starts, it uses the SIOCGIFCONF ioctl to find
directly connected interfaces configured into the system and
marked up (the software loopback interface is ignored). If
there are multiple interfaces, 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 interface supports it) and enters a loop, listening
for request and response packets from other hosts.
When it receives a request packet, routed formulates a reply
based on the information maintained in its internal tables.
The response packet it generates 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 is relative to the
sender.
routed uses response packets it receives to update the
routing tables if one of the following conditions is
satisfied:
1. There is no routing table entry for the destination
network or host, and the metric indicates the destination
is ``reachable'' (i.e., 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 same inter-network
router which is routing the packets for the destination.
3. The existing entry in the routing table has not been
updated for 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
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destination than the one currently stored in the routing
tables; this is determined by comparing the metric of the
new route to the one stored in the table.
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 up to
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 three minutes, the entry's metric
is set to infinite and marked for deletion. routed waits an
additional 60 seconds before deleting to ensure that the
invalidation is propagated throughout the internet.
Hosts acting as inter-network routers gratuitously supply
their routing tables every 30 seconds to all directly
connected hosts and networks.
-s forces routed to supply routing information whether it
is acting as an inter-network router or not
-q is the opposite of the -s option.
-t prints on the standard output all packets sent or
received. In addition, routed will not divorce itself
from the controlling terminal so that interrupts from
the keyboard will kill the process.
logfile
the name of file in which routed's actions should be
logged. This log contains any changes to the routing
tables and a history of recent messages sent and
received relating to the changed route.
In addition to the facilities described above, routed
supports the notion of ``distant'' passive and active
gateways. When routed starts up, it reads the file
/etc/gateways to find gateways which may not be identified
using the SIOGIFCONF 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 (i.e.,
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 information transmitted. Active
gateways are treated equally to network interfaces. Routing
information is distributed to the gateway and if no routing
information is received for a period of the time, the
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associated route is deleted.
/etc/gateways is a series of lines, each in the following
format:
net/host name1 gateway name2 metric value passive/active
The net or host keyword indicates if the route is to a
network or specific host.
name1 is the name of the destination network or host. This
may be a symbolic name located in /etc/networks or
/etc/hosts, or an Internet address specified in ``dot''
notation; see inet(3N).
name2 is the name or address of the gateway to which
messages should be forwarded.
value is a metric indicating the hop count to the
destination host or network.
The keyword passive or active indicates if the gateway
should be treated as passive or active (as described above).
FILES
/etc/routed
/etc/gateways
SEE ALSO
udp(5P).
Internet Transport Protocols, XSIS 028112, Xerox System
Integration Standard.
BUGS
The kernel's routing tables may not correspond to those of
routed for short times 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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