© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.1 Routing Working at a Small-to-Medium Business or ISP – Chapter 6

2 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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.

3 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

4 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Enabling Routing Protocols  Components of a route: destination value, subnet mask, gateway, route cost or metric

5 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Enabling Routing Protocols  Directly connected routes  Static routes  Dynamically updated routes  Default route

6 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Enabling Routing Protocols  Static routes are manually configured  Static routes are suitable for small networks with few changes

7 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

8 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Enabling Routing Protocols Routing Information Protocol (RIP):  RFC 1058  Distance vector using hop count metric  Updates every 30 seconds

9 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Enabling Routing Protocols Enhanced Interior Gateway Routing Protocol: (EIGRP)  Enhanced distance vector protocol  Uses a variety of metrics  Cisco-proprietary

10 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Enabling Routing Protocols Characteristics of link-state protocols:  Full database of distant routers and interconnections  Link-state advertisements  Topological database  SPF algorithm

11 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Enabling Routing Protocols Open Shortest Path First (OSPF):  Non-proprietary  Link-state  RFC 2328  Advanced protocol

12 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Enabling Routing Protocols Criteria for choosing routing protocols:  Ease of management  Ease of configuration  Efficiency

13 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Enabling Routing Protocols  Describe and implement RIP routing on an integrated router

14 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

15 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

16 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Exterior Routing Protocols  Each AS uses dedicated border gateway routers to route packets across the Internet

17 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Exterior Routing Protocols  ISPs use exterior routing protocols to forward or control local and/or transit traffic  Exterior protocols enforce policies and support reliability

18 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Exterior Routing Protocols Configuring Border Gateway Protocol (BGP):  Configure the AS number  Identify ISP neighbor router

19 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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.

20 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public