HP-UX Reference (11i v1 00/12) - 4 File Formats (vol 8)

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STANDARD Printed by: Nora Chuang [nchuang] STANDARD

/build/1111/BRICK/man4/!!!intro.4

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gated.conf(4) gated.conf(4)

martians {

0.0.0.26

};

The statements in the sample perform the following functions:

• The options statement tells the system to generate a default route when it peers with an EGP or

BGP neighbor.

• The autonomoussystem statement tells GateD to use AS number 249 for in EGP and BGP.

• The interface statement tells GateD not to mark interface 128.66.12.2 as down even if it sees no

trafﬁc.

• The martians statement prevents routes to 0.0.0.26 from ever being accepted.

Protocol Overview

Routing protocols determine the "best" route to each destination and distribute routing information among

the systems on a network. Routing protocols are divided into two general groups: interior and exterior pro-

tocols. GateD software combines management of the interior and exterior routing protocols in one software

daemon.

Interior Routing Protocols

Interior protocols are used to exchange reachability information within an autonomous system (AS). They

are referred to as a class by the acronym igp. There are several interior protocols:

RIP The Routing Information Protocol, Version 1 and Version 2, is the most commonly used interior proto-

col. RIP selects the route with the lowest metric as the best route. The metric is a hop count

representing the number of gateways through which data must pass to reach its destination. The long-

est path that RIP accepts is 15 hops. If the metric is greater than 15, a destination is considered

unreachable and GateD discards the route. RIP assumes the best route is the one that uses the fewest

gateways which is the shortest path, not taking into account congestion or delay on route.

The RIP version 1 protocol is described in RFC 1058 and the RIP version 2 protocol is described in

RFC 1388.

HELLO

HELLO , another interior protocol, uses delay as the deciding factor in choosing the best route.

Round-trip time is the length of time it takes a datagram to travel from the source and destination.

HELLO is historically signiﬁcant for the Internet as it was the protocol used among the original proto-

type NSFNET backbone fuzzball gateways. Today, like fuzzballs, HELLO is a little-used protocol.

An earlier version of the HELLO protocol is described in RFC 891.

OSPF

Open Shortest Path First is a link-state protocol. OSPF is better suited than RIP for complex net-

works with many routers. OSPF provides equal cost multipath routing.

OSPF is described in RFC 1583, the MIB is deﬁned in RFC 1253. Other related documents are RFC

1245, RFC 1246 and RFC 1370.

Exterior Routing Protocols

Exterior protocols are used to exchange routing information between autonomous systems. Exterior proto-

cols are only required when an autonomous system must exchange routing information with another auto-

nomous system. Routers within an autonomous system run an interior routing protocol like RIP. Only

those gateways that connect an autonomous system to another autonomous system need to run an exterior

routing protocol. There are two exterior protocols currently supported by GateD:

EGP

Exterior Gateway Protocol: Originally EGP reachability information was passed into

ARPANET/MILNET "core" gateways where the best routes were chosen and passed back out to all

connected autonomous systems. As the Internet moved toward a less hierarchical architecture, EGP,

an exterior routing protocol which assumes a hierarchical structure, became less effective.

The EGP protocol is described in RFC 827 and RFC 904.

BGP

Border Gateway Protocol is replacing EGP as the exterior protocol of choice. BGP exchanges reacha-

bility information between autonomous systems, but provides more capabilities than EGP. BGP uses

Section 4−−82 − 11 − HP-UX Release 11i: December 2000

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