Extreme networks Summit1 Manuale Utente

10-2

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UMMIT

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NSTALLATION

 

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OUTING

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ROTOCOLS

The distinction between RIP and OSPF lies in the fundamental differences between 
distance vector protocols and link state protocols. Using a distance vector protocol, each 
router creates a unique routing table from summarized information obtained from 
neighboring routers. Using a link state protocol, every router maintains an identical 
routing table created from information obtained from all routers in the autonomous 
system. Each router builds a shortest path tree, using itself as the root. The link state 
protocol ensures that updates sent to neighboring routers are acknowledged by the 
neighbors, verifying that all routers have a consistent network map.

The biggest advantage of using RIP is that it is relatively simple to understand and 
implement, and it has been the de facto routing standard for many years.

RIP has a number of limitations that can cause problems in large networks, including 
the following:

A limit of 15 hops between the source and destination networks

A large amount of bandwidth taken up by periodic broadcasts of the entire routing 
table

Slow convergence

Routing decisions based on hop count; no concept of link costs or delay

Flat networks; no concept of areas or boundaries

OSPF offers many advantages over RIP, including the following:

No limitation on hop count

Route updates multicast only when changes occur

Faster convergence

Support for load balancing to multiple routers based on the actual cost of the link

Support for hierarchical topologies where the network is divided into areas

The details of RIP and OSPF are explained later in this chapter.

Summit.bk : 10PROT.FM  Page 2  Thursday, June 18, 1998  9:27 AM