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7/31/2019 25.1_Determining IP Routes
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2002, Cisco Systems, Inc. All rights reserved.
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2002, Cisco Systems, Inc. All rights reserved. 2
Determining IP Routes
Module 5
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Objectives
Upon completing this lesson, you will be able to:
Describe the features and operation of static routing
Describe the features and operation of dynamic routingprotocols, including RIP, IGRP, EIGRP,and OSPF
Build a functional router configuration to support thespecified network operational requirements, given anetwork design
Use show commands to identify anomalies in routingoperation, given an operational router
Use debug commands to identify events and anomalies inrouting operation, given an operational router
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Routing Overview
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Objectives
Upon completing this lesson, you will beable to:
Explain the differences between static routingand dynamic routing
Identify the classes of routing protocols
Use Cisco IOS commands to configure staticroutes and default route forwarding, given a
functioning router Use show commands to identify anomalies in
static routing operation, given an operationalrouter
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To route, a router needs to do the following:
Know the destination address
Identify the sources it can learn from
Discover possible routes
Select the best route
Maintain and verify routing information
What Is Routing?
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Routers must learn destinations that are
not directly connected.
What Is Routing? (Cont.)
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Static Route
Uses a route that anetwork administratorenters into the routermanually
Dynamic Route
Uses a route that anetwork routingprotocol adjustsautomatically for
topology or trafficchanges
Identifying Static and Dynamic Routes
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Static Routes
Configure unidirectional static routes to and froma stub network to allow communications to occur.
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Defines a path to an IP destination network or subnet or host
Router(config)#ip route network [mask]
{address
|interface
}[distance
] [permanent]
Static Route Configuration
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Static Route Example
This is a unidirectional route. You must have a route
configured in the opposite direction.
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Default Routes
This route allows the stub network to reach all known
networks beyond router A.
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Verifying the StaticRoute Configuration
router#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
U - per-user static route
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
10.0.0.0/8 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, Serial0S* 0.0.0.0/0 is directly connected, Serial0
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Routing protocols areused between
routers to determinepaths and maintainrouting tables.
Once the path isdetermined, a router canroute a routed protocol.
What Is a Routing Protocol?
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An autonomous system is a collection of networksunder a common administrative domain.
IGPs operate within an autonomous system.
EGPs connect different autonomous systems.
Autonomous Systems: Interior orExterior Routing Protocols
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Administrative Distance:Ranking Routes
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Determining the route AdministrativeDistance
AD is a number that measures thetrustworthiness of the source of a routinginformation.
The higher the number, the lower thetrustworthiness rating.
Example:Directed connection 0
Static route (by default) 1IGRP 100OSPF 110RIP 120
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Classes of Routing Protocols
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Classful Routing Overview
Classful routing protocols do not include thesubnet mask with the route advertisement.
Within the same network, consistency of thesubnet masks is assumed.
Summary routes are exchanged between foreignnetworks.
Examples of classful routing protocols:RIP Version 1 (RIPv1)
IGRP
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Classless Routing Overview
Classless routing protocols include the subnet maskwith the route advertisement.
Classless routing protocols support variable-lengthsubnet masking (VLSM).
Summary routes can be manually controlled withinthe network.
Examples of classless routing protocols:
RIP Version 2 (RIPv2)
EIGRP
OSPF
IS-IS
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Routing ProtocolComparison Chart
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Using the ip classless Command
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Without ip classless command
BHMGAD
S0/0
192.168.13.2
To
10.2.2.4
192.168.1.4/30
10.1.1.0
10.3.3.0
Fa0/1
Fa0/0
Destination network Outbound interface
10.3.3.0 Fa0/1
10.1.1.0 Fa0/0
0.0.0.0 S0/0
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With ip classless command
BHMGAD
S0/0
192.168.13.2
To
10.2.2.4
192.168.1.4/30
10.1.1.0
10.3.3.0
Fa0/1
Fa0/0
Destination network Outbound interface
10.3.3.0 Fa0/1
10.1.1.0 Fa0/0
0.0.0.0 S0/0
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Summary
Routing is the process by which an item gets from onelocation to another. In networking, a router is the deviceused to route traffic.
Routers can forward packets over static routes or
dynamic routes, based on the router configuration. Static routes can be important if the Cisco IOS software
cannot build a route to a particular destination. Staticroutes are also useful for specifying a gateway of lastresort to which all unroutable packets will be sent.
A default route is a special type of static route used forsituations when the route from a source to a destinationis not known or when it is unfeasible for the routing tableto store sufficient information about the route.
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