HP-UX Routing Services Administrator's Guide HP-UX 11i v2, HP-UX 11i v3 (B2355-91153, November 2011)

In large local networks, multiple paths often exist to other parts of the local network. You can use
gated to maintain nearly optimal routing to other parts of the local network, and to recover from
link failures.
Advantages
gated offers the following advantages:
• Dynamic routing eliminates the need to reset routes manually. When network failures occur,
routes are automatically rerouted.
• Dynamic routing facilitates adding and administering nodes.
• Dynamic routing lowers the cost of operating complex Internet systems.
• gated translates among several protocols, passing information within or between IP routing
domains or autonomous systems. Autonomous system (AS) is used here to refer to a group of
connected nodes and routers in the same administrative domain that exchange routing
information via a common routing protocol.
• gated provides the system administrator flexibility in setting up and controlling network
routing. For example, gated can listen to network traffic at specified routers, determine
available routes, and update local routing tables accordingly.
Deciding When to Use gated
gated is mostly used in large networks, or in small networks connected to larger wide area
networks.
You must run gated on routers (gateways) to send the routing information to other routers. gated
supports many routing protocols that allow routers to build and maintain dynamic routing tables.
However, gated also supports RIP, which runs on end systems (systems with only one network
interface) as well as on routers.
NOTE: gated also supports RDP as a client. RDP will replace rdpd.
gated is useful in topologies with multiple routers and multiple paths between parts of the network.
gated allows routers to exchange routing information and to change routing information
dynamically to reflect topology changes and maintain optimal routing paths.
Alternatively, you can configure IP routes manually with the route (1M) command. For end
systems in subnets with only one router (gateway) to the Internet, manually configuring a default
route is usually more efficient than running gated. For more details on manually manipulating the
routing tables, type man 1M route at the HP-UX prompt.
When connected to wide area networks, you can use gated to inject local routing information
into the wide area network’s routing table.
Routing Protocols
For routing purposes, networks and gateways are logically grouped into autonomous system (AS).
Companies and organizations that want to connect to the Internet and form an AS must obtain a
unique AS number from the Internet Assigned Numbers Authority (IANA).
An interior gateway protocol distributes routing information within the autonomous system. An
exterior gateway protocol distributes general routing information about an autonomous system to
other autonomous systems.
Dividing networks into autonomous systems keeps route changes inside the autonomous system
from affecting other autonomous systems. When routes change within an autonomous system, the
new information need not be propagated outside the autonomous system if it is irrelevant to
gateways outside the autonomous system.
The gated Routing Daemon 11