routed(8)

NAME

routed - network routing daemon

SYNOPSIS

routed [-d] [-g] [-s] [-q] [-t] [-p] [-i device] [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 Infor
mation Proto col in maintaining up to date kernel routing table entries.
It used 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(4) socket for
the route(8) service (see services(5)) 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(2) to
find those directly connected interfaces configured into the system and
marked ``up'' (the software loopback interface is ignored). If
multiple inter faces are present, it is assumed that the host will forward
packets
between networks. Routed then transmits a request packet on
each inter face (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 gen erated contains a list of known routes, each marked with a
``hop count'' metric (a count of 16, or greater, is considered ``infi
nite''). The met ric 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 net
work or host,and the metric indicates the destination is ``reach
able'' (i.e. the hop count is not infinite).
2. The source host of the packet is the same as the router
in theexisting routing table entry. That is, updated infor
mation 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 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 updates the kernel routing table. The change is
reflected in the next response packet sent.
In addition to processing incoming packets, routed also pe
riodically 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 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 capa
ble 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 in
terface, another route may be chosen to route around the interface,
or the route may be dropped if no alternative is available.
Options supported by routed:
-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 rout
ing information that it is acting as an internetwork router. This
is the default if multiple network interfaces are present, or if a
point-topoint 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.
-p this option forces routed to ignore existence of all
point-topoint network interfaces. Routed wont send nor re
ceive routing updates through these interfaces and also wont prop
agate corre sponding routes to remote endpoints directly reach
able through them. Sometimes it is not desirable to send/receive
routing information about routes through such interfaces,
for example when point-to-point link with proxy-arp is in use.
-i dev this option forces routed to ignore existence of a
specified net
work interface dev. Similarly to -p flag, routed
wont send nor
receive routing updates through dev, nor it will ad
vertise direct routes via such interface.
Any other argument supplied is interpreted as the full path
to and 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. With first event to be
logged, routed will
create log file in "/var/log/routed" directory (which has to
exist and be readable/writeable only by root). For security reasons, this
argument has
to begin with "/var/log/routed", as routed itself does not
perform other security checks towards validity of the remote
traceon/traceoff requests it may receive. Unless for debugging purposes, it is strong
ly recommended that the logging path itself does not exist nor is specified
as routed
parameter at all.
In addition to the facilities described above, routed sup
ports the notion of ``distant'' passive , active , external and announced
gateway types.
When routed is started up, it reads the file /etc/gateways
to find gate ways which may not be located using only information from
the SIOGIFCONF ioctl(2). 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 informa
tion (i.e.
they should have a routed process running on the machine).
Routes through passive gateways are installed in the ker
nel's routing
tables by routed once upon its startup. Such routes are not
included in any routing information transmitted.
Active gateways are treated equally to network interfaces.
Routing
information is distributed to the gateway and routed listens
for updates on the interface that the gateway is reachable through.
Gateways marked external are also passive, but are not
placed in the ker nel routing table nor are they included in routing updates.
The function
of external entries is to inform routed that another routing
process will install such a route, so that it should not install alter
nate routes to that destination. Such entries are only required when both
routers may learn of routes to the same destination.
Routes to networks through gateways marked as announced will
be included in each routing advertisement, but won't be installed in the
kernel rout ing table. This kind of entries is only required for the
gateways that are directly reachable, but are unable to announce their
routes, so that the rest of the RIP1 protocol-equipped network will know
about such
routes too. Entries of announced type can also be used to
announce direct routes for own interfaces, that didn't exist at the time
when routed has
been started, but can be expected to come up later (such as
routes for point-to-point interfaces).
The /etc/gateways is comprised of a series of lines, each in
the follow ing format:
<net | host> name1 gateway name2 metric value <passive
active
external | announced>
The net or host keyword indicates if the route is to a net
work or spe cific host.
Name1 is the name of the destination network or host. This
may be a sym bolic name located in /etc/networks or /etc/hosts (or, if
started after named(8), known to the name server), or an Internet address
specified in ``dot'' notation; see inet(3).
Name2 is the name or address of the gateway to which mes
sages should be forwarded.
Value is a metric indicating the hop count to the destina
tion host or network.
One of the keywords passive, active, external or announced
indicates if the gateway should be treated as passive or active (as de
scribed above),
whether the gateway is external to the scope of the routed
protocol, or whether the route reachable via such gateway should be in
cluded in the routing table announcements.
Internetwork routers that are directly attached to the
Arpanet or Milnet should use the Exterior Gateway Protocol (EGP) to gather
routing informa tion rather than using a static routing table of passive
gateways. EGP is required in order to provide routes for local networks to
the rest of the Internet system.

FILES

/etc/gateways for distant gateways

BUGS

Routed is heavily 32bit architecture dependant. You should
eventually consider using gated(8) or zebra(8).
The kernel's routing tables may not correspond to those of
routed when
redirects change or add routes. Routed should note any
redirects received by reading the ICMP packets received via a raw
socket.
Routed also doesn't notice of any new interface, that didn't
exist prior to its start, but has newly appeared and come to ``up''
state after routed has been started, and won't announce route for such
interface.
Routed should incorporate other routing protocols. Using
separate pro cesses for each requires configuration options to avoid re
dundant or com peting routes.
Routed should listen to intelligent interfaces, such as an
IMP, to gather more information. It does not always detect unidirectional
failures in network interfaces (e.g., when the output side fails).

HISTORY

The routed command appeared in 4.2BSD.
Linux NetKit (0.18) December 11, 1993 Linux

docs.sk

comprehensive documentation repository

See also

routed(8)

NAME

SYNOPSIS

DESCRIPTION

FILES

SEE ALSO

BUGS

HISTORY