Routing Protocol Principles and Configuration: A Comprehensive Guide, Lecture notes of Computer Network Management and Protocols

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ZXR10_II_08_

Routing Protocol Principle and

Configuration

V1.

Course Outline

• (^) Route and Routing Table
• (^) Routing Protocol Principle
• (^) Common Routing Protocol Overview

Routing Table

GAR#show ip route IPv4 Routing Table: Dest Mask Gw Interface Owner pri metric 10.26.32.0 255.255.255.0 10.26.245.5 fei_1/1 bgp 200 0 10.26.33.253 255.255.255.255 10.26.245.5 fei_1/1 ospf 110 14 10.26.33.254 255.255.255.255 10.26.245.5 fei_1/1 ospf 110 13 10.26.36.0 255.255.255.248 10.26.36.2 gei_5/2.1 direct 0 0 10.26.36.2 255.255.255.255 10.26.36.2 gei_5/2.1 address 0 0 10.26.36.24 255.255.255.248 10.26.36.26 gei_5/2.4 direct 0 0 10.26.245.4 255.255.255.252 10.26.245.6 fei_1/1 direct 0 0 10.26.245.6 255.255.255.255 10.26.245.6 fei_1/1 address 0 0

Route Owner Classification

 Direct route

 It is the segment address configured on the interface

directly falls into the routing table and related to

interface, discovered by data-link layer. The

disadvantage is that only the segment where the

interface belongs to can be discovered.

 Static route

 It is the route configured manually by administrator,

which does not change with the network topology. The

disadvantage is that there is more pressure on

administrator.

 Dynamic route

 It is generated from dynamic route protocols and able

to change with the network topology. It is used in large

scale and complicated networks.

Static Route  (^) The route configured manually by administrator is called static route, which is generally preset when installed the system and it does not change with the network topology automatically.

Default Route

 (^) The default route is an item in the routing table, used to designate how to forward the data unit without a definite next hop address. The packets without definite route items in the routing table will be all forwarded through the interface and next hop address designated by the default route.

Metric

 The cost to reach the destination

E1 56

E

B

A

Hop count Hop count

RIP

Metric Calculation

 (^) The common path characters used for metric calculation are described below:  (^) Hop count: the total number of routes the packet has to pass through. The less the hop count is, the better the route is. The path is usually described by the hop count for getting to the destination.  (^) Bandwidth: the capacity of link for transmitting the data.  (^) Delay: the time need for sending the data from SA to DA.  (^) Load: the activity quantity on the network resources, e.g. router and links.  (^) Reliability: refers to the error factor in each network links.  (^) MTU: refers to the MTU the port able to send.  (^) Each route protocol selects the above one or more characters for metric calculation.  (^) There is no comparison between the metrics of different route protocols.

Course Outline

• (^) Route and Routing Table
• (^) Routing Protocol Principle
• (^) Common Routing Protocol Overview

For dynamic routes, an administrator no longer needs to manually maintain the routing table. Instead, it is only necessary to run certain route protocol on each router. The routing protocols will generate route items in the routing table according to the interface configuration (e.g. IP address configuration) and the state of link it connecting to. Dynamic Route Protocol

Distance-Vector and Link State Routing Protocols

 Distance-vector routing protocol: The representative

is RIP. Neighbor routers exchange the whole routing

table and superimpose vectors to know the whole

routing table.

 Link state routing protocols include OSPF, IS-IS and

so on. Link state is hierarchical. The router using this

algorithm does not simply learns routes from

neighbors. It divides routers in different areas and

collects the link state information of all routers in an

area. Each router generates a network topology

according to the link state information and then

calculates the routes according to the topology.

Autonomous System 65000 Autonomous System 65500 IGPs: RIP, OSPF ISIS EGPs: BGP ， EGP  (^) an AS is set of networks with the same technology management.  (^) IGPs run in an area.  (^) EGPs connect different ASs. EGP and IGP

Cooperation between Routing Protocols

 Each routing protocol only advertises and learns the

protocols it knows. To know other routes, it is

necessary to use redistribution operation.

 “Redistribute” means: The router looks up local

routing table. If there is any route to be introduced

in, the protocol advertises the route as a route it

knows.

Performance Indicators for Dynamic Routing Protocols

RIP 1 IGRP RIP 2 EIGRP IS-IS OSPF BGP comprehensive performance RIP 1 IGRP RIP 2 EIGRP IS-IS OSPF BGP With route self-loop Without route self-loop