gateways - Specifies Internet routing information to the
routed daemon
/etc/gateways
The /etc/gateways file identifies gateways for the routed
daemon. Ordinarily, the routed daemon queries the network
and builds routing tables. The routed daemon builds the
tables from routing information transmitted by other hosts
directly connected to the network. However, there may be
gateways that this command cannot identify through its
queries. These unidentified gateways are known as distant
gateways. Such gateways should be identified in the
/etc/gateways file, which the routed daemon reads when it
starts.
The general format of an file entry in the /etc/gateways
file is: Destination Name1 gateway Name2 metric Value Type
The following is a brief description of each element in an
/etc/gateways file entry: A keyword that indicates whether
the route is to a network or to a specific host. The two
possible keywords are net and host. The name associated
with Destination. Name1 can be either a symbolic name (as
used in the /etc/hosts or /etc/networks file) or an Internet
address specified in dotted-decimal format. An indicator
that the following string identifies the gateway
host. The name or address of the gateway host to which
messages should be forwarded. An indicator that the next
string represents the hop count to the destination host or
network. The hop count, or number of gateways, from the
local network to the destination network. A keyword that
indicates whether the gateway should be treated as active,
passive, or external. The three possible keywords are as
follows: An active gateway is treated like a network
interface. That is, it is expected to exchange RIP (Routing
Information Protocol) routing information. Information
about it is maintained in the internal routing tables as
long as it is active and is included in any routing information
that is transmitted through RIP. If it does not
respond for a period of time, the route associated with it
is deleted from the internal routing tables. A passive
gateway is not expected to exchange RIP routing information.
Information about it is maintained in the routing
tables indefinitely and is included in any routing information
that is transmitted through RIP. An external gateway
is identified to inform the routed daemon that another
routing process will install such a route and that alternative
routes to that destination should not be installed.
Information about external gateways is not maintained in
the internal routing tables and is not transmitted through
RIP.
Note that these routes must be to networks.
To specify a route to a network through a gateway host
with an entry in the gateways file, enter: net net2 gateway
host4 metric 4 passive
This example specifies a route to a network, net2,
through the gateway host4. The hop count metric to
net2 is 4, and the gateway is treated as passive.
To specify a route to a host through a gateway host
with an entry in the gateways file, enter: host
host2 gateway host4 metric 4 passive
This example specifies a route to a host, host2,
through the gateway host4. The hop count metric to
host2 is 4, and the gateway is treated as passive.
To specify a route to a host through an active
Internet gateway with an entry in the gateways
file, enter: host host10 gateway 192.100.11.5 metric
9 active
This example specifies a route to a specific host,
host10, through the gateway 192.100.11.5. The hop
count metric to host10 is 9 and the gateway is
treated as active. To specify a route to a host
through a passive Internet gateway with an entry in
the gateways file, enter: host host10 gateway
192.100.11.5 metric 9 passive
This example specifies a route to a specific host,
host10, through the gateway 192.100.11.5. The hop
metric count to host10 is 9 and the gateway is
treated as passive. To specify a route to a network
through an external gateway, enter a line in
the following format: net net5 gateway host7 metric
11 external
This example specifies a route to a network, net5,
through the gateway host7. The hop count metric to
net5 is 11 and the gateway is treated as external
(that is, it is not advertised through RIP, but is
advertised through an unspecified routing protocol).
Daemons: gated(8), routed(8)
gateways(4)
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