Routing
Working at a Small-to-Medium Business or ISP –
Chapter 6
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Objectives
 Describe the purpose and function of dynamic routing
and the protocols used to implement it.
 Configure RIPv2 dynamic routing using the Cisco
IOS.
 Describe the use of exterior routing protocols across
the Internet.
 Enable BGP on a customer site router.
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Enabling Routing Protocols
 Routing tables contain locally connected
networks
 Routers use routing tables to determine routes
 Routes can be statically assigned or
dynamically learned through routing protocols
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Enabling Routing Protocols
 Components of a route: destination value,
subnet mask, gateway, route cost or metric
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Enabling Routing Protocols
 Directly connected routes
 Static routes
 Dynamically updated routes
 Default route
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Enabling Routing Protocols
 Static routes are manually configured
 Static routes are suitable for small networks
with few changes
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Enabling Routing Protocols
Characteristics of distance vector protocols:
 Routers share copies of routing tables
 Distance metric can be based on hops, cost,
bandwidth, speed, delay or reliability
 Vector is the address of the next hop along a
route
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Enabling Routing Protocols
Routing Information Protocol (RIP):
 RFC 1058
 Distance vector using hop count metric
 Updates every 30 seconds
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Enabling Routing Protocols
Enhanced Interior Gateway Routing Protocol:
(EIGRP)
 Enhanced distance vector protocol
 Uses a variety of metrics
 Cisco-proprietary
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Enabling Routing Protocols
Characteristics of link-state protocols:
 Full database of distant routers and
interconnections
 Link-state advertisements
 Topological database
 SPF algorithm
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Enabling Routing Protocols
Open Shortest Path First (OSPF):
 Non-proprietary
 Link-state
 RFC 2328
 Advanced protocol
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Enabling Routing Protocols
Criteria for choosing routing protocols:
 Ease of management
 Ease of configuration
 Efficiency
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Enabling Routing Protocols
 Describe and implement RIP routing on an
integrated router
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Exterior Routing Protocols
 The Internet is divided into autonomous
systems
 AS: a set of networks controlled by a single
administration using the same internal routing
policy
 Each ISP is an AS
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Exterior Routing Protocols
 Interior gateway protocols (IGPs) exchange
routing information within an AS or individual
organization
 Exterior gateway protocols (EGPs) exchange
routing information between autonomous
systems
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Exterior Routing Protocols
 Each AS uses dedicated border gateway
routers to route packets across the Internet
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Exterior Routing Protocols
 ISPs use exterior routing protocols to forward
or control local and/or transit traffic
 Exterior protocols enforce policies and support
reliability
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Exterior Routing Protocols
Configuring Border Gateway Protocol (BGP):
 Configure the AS number
 Identify ISP neighbor router
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Summary
 All routers make routing decisions by looking up information stored
in their routing tables.
 Routes can be statically assigned by an administrator, or
dynamically learned by the router via a routing protocol.
 Routing protocols use either distance-vector or link-state
algorithms to calculate the best routes to each destination.
 Criteria such as ease of management, ease of configuration, and
efficiency must be considered when selecting a routing protocol for
use within an organization.
 Organizations are also called Autonomous Systems.
 Between Autonomous Systems, Exterior Gateway routing
protocols control the flow of traffic.
 ISPs handle Internet traffic through the use of routing policies.
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