Routing allows traffic from your local network to reach its
destination elsewhere on the internet. All hosts and gateways
on a network use routing protocols to exchange and store routing
information. Routing is simply the act of forwarding datagrams
based on information stored in a routing table.
The TCP/IP Services product provides two types of routing:
o Static
Because static routing requires manual configuration, it is
most useful when the number of gateways is limited and where
routes do not change frequently.
o Dynamic
Dynamic routing tables use information received by means of
routing protocol updates; when routes change, the routing
protocol provides information on the changes. Routing daemons
implement a routing policy, that is, the set of rules that
decide which routes go in to the routing table. A routing
daemon writes routing messages to a routing socket causing the
kernel to add a new route, delete an existing route, or modify
an existing route.
The kernel also generates routing messages that can be read by
any routing socket when events occur that might be of interest
to the process; for example, when the interface has gone down
or a redirect has been received.
TCP/IP Services implements two routing daemons: the Routing
Daemon (ROUTED) and the Gateway Routing Daemon (GATED).
1 – ROUTED
ROUTED supports the Routing Information Protocol (RIP). Use
TCPIP$CONFIG to enable ROUTED.
2 – GATED
GATED supports interior and exterior gateway protocols. It
obtains information from several routing protocols and selects
the best routes based on that information.
Before enabling GATED, you must configure the GATED protocols
by editing the file TCPIP$GATED.CONF. Use TCPIP$CONFIG to enable
dynamic routing.
2.1 – GATED Protocols
You can configure GATED to use one or more of the following
protocols:
Protocol RFC Description
Routing Information RFC RIP is a commonly used interior
Protocol (RIP) 1058, protocol that selects the route
Versions 1 and 2 RFC 1723 with the lowest metric (hop
count) as the best route.
Open Shortest Path RFC 1583 Another interior routing
First (OSPF) Version protocol, OSPF is a link-state
2 protocol (shortest path first)
and better suited than RIP
foruse in complex networks with
many routers.
Exterior Gateway RFC 904 EGP exchanges reachability
Protocol (EGP) information between autonomous
systems. An autonomous system
is usually defined as a set
of routers under a single
administration, using an
interior gateway protocol and
common metric to route packets.
Autonomous systems use exterior
routing protocols to route
packets to other autonomous
systems.
Border Gateway RFCs Like EGP, BGP exchanges
Protocol (BGP) 1163, reachability information
1267, between autonomous systems
1771 but supports nonhierarchical
topologies. BGP uses path
attributes to provide more
information about each route.
Path attributes can include,
for example, administrative
preferences based on political,
organizational, or security
considerations.
Router Discovery RFC 1256 This protocol is used to inform
hosts of the availability of
hosts it can send packets to
and to supplement a statically
configured default router.