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

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

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

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

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

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

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

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

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

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

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

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

19. 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.