Cabletron Systems CyberSWITCH CSX500 Specifications download pdf (Page 144)

Configuration with QuickSET

128 QuickSET Configuration Guide

Next Hop

Entries in RIP-2 routing tables always have a Next Hop ﬁeld. The Next Hop is the IP address of the

next router along the path to the destination. The purpose of the Next Hop in the routing table is to

prevent packets from being routed through extra hops in the system. The limitation of a maximum

network diameter of 15 hops for the Next Hop ﬁeld is common to both RIP-1 and RIP-2. This

statement of the limit assumes that a cost of 1 is used for each network (see Metrics, below). The

Next Hop ﬁeld will contain a number between 1 and 15 inclusive. A number of 16 means that the

network is unreachable.

Metrics

The RIP-1 and RIP-2 protocols use ﬁxed “metrics” to compare alternative routes. This is not

appropriate where routes need to be chosen based on real-time parameters such as measured delay,

reliability, or load. RIP is intended to allow routers to exchange information for computing routes

through an IP-based network. Any router that uses RIP is assumed to have interfaces to one or

more networks, otherwise it isn't a router. These are referred to as directly connected networks.

The RIP protocol relies on access to certain information about each of these networks, the most

important of which is its metric. This metric represents the total “cost” of getting a datagram from

the router to that destination.

The routing table has the entries listed below for each destination that is reachable:

• The IP preﬁx of the destination

• A metric, described above

• The IP address of the next router along the path (the Next Hop)

• A ﬂag to indicate the information about the route has changed recently

• Various timers associated with the route

Split Horizon

Split Horizon is an algorithm for avoiding problems caused by including routes in the updates sent

to the gateway from which they were learned. The basic split horizon algorithm omits routes

learned from one neighbor in updates sent to that neighbor.

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Cabletron Systems CyberSWITCH CSX500 Specifications Page 144