Overview

The gated Routing Daemon

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.

gated supports the following interior gateway protocols, as defined in IETF RFCs:

•Routing Information Protocol (RIP) is a common routing protocol used within an autonomous system. A de facto industry standard, it is also used by routed, a service distributed by Berkeley. RIP is not intended for use in wide area network (WAN) applications. There are currently two versions of RIP implementations: Version 1, as defined in RFC 1058, and Version 2, as defined in RFC 1388. gated supports all Version 1 features and most of the features of Version 2. The following Version 2 features are not supported: RIP management information base (MIB) route tag, and route aggregation. gated 3.5.9 supports authentication.

•Open Shortest Path First (OSPF), similar to RIP, is a routing protocol that allows routing information to be distributed between routers in an autonomous system. Each router on the network transmits a packet that describes its local links to all other routers. The distributed database is then built from the collected descriptions. If a link fails, updated information floods the network, allowing all routers to recalculate their routing tables at the same time. OSPF is more suitable than RIP for routing in complex networks with many routers. gated 3.0 supports most of the features of OSPF Version 2, as described in RFC 1247, except the IP type of service (TOS) routing feature. Equal cost multipath routes are limited to one hop per destination, because the HP-UX kernel supports only one gateway per route.

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Chapter 1