Working at a Small-to-Medium Business or ISP – Chapter 6 Routing Working at a Small-to-Medium Business or ISP – Chapter 6

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.

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

Enabling Routing Protocols Components of a route: destination value, subnet mask, gateway, route cost or metric

Enabling Routing Protocols Directly connected routes Static routes Dynamically updated routes Default route

Enabling Routing Protocols Static routes are manually configured Static routes are suitable for small networks with few changes

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

Enabling Routing Protocols Routing Information Protocol (RIP): RFC 1058 Distance vector using hop count metric Updates every 30 seconds

Enabling Routing Protocols Enhanced Interior Gateway Routing Protocol: (EIGRP) Enhanced distance vector protocol Uses a variety of metrics Cisco-proprietary

Enabling Routing Protocols Characteristics of link-state protocols: Full database of distant routers and interconnections Link-state advertisements Topological database SPF algorithm

Enabling Routing Protocols Open Shortest Path First (OSPF): Non-proprietary Link-state RFC 2328 Advanced protocol

Enabling Routing Protocols Criteria for choosing routing protocols: Ease of management Ease of configuration Efficiency

Enabling Routing Protocols Describe and implement RIP routing on an integrated router

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

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

Exterior Routing Protocols Each AS uses dedicated border gateway routers to route packets across the Internet

Exterior Routing Protocols ISPs use exterior routing protocols to forward or control local and/or transit traffic Exterior protocols enforce policies and support reliability

Exterior Routing Protocols Configuring Border Gateway Protocol (BGP): Configure the AS number Identify ISP neighbor router

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.