1. CCNA 2 Week 6 Routing Protocols

2. Copyright © 2005 University of Bolton Topics Static Routing Dynamic Routing Routing Protocols Overview

3. Copyright © 2005 University of Bolton Introduction to Routing Routing is the process used by a router to forward packets towards the destination network To make decisions routers learn about remote networks Dynamic routing - information is learned from other routers Static routing - network administrator configures network information manually

4. Copyright © 2005 University of Bolton Adding Static Routes In Global Config mode: –ip route net_addr netmask gateway –ip route 10.0.0.0 255.0.0.0 s1/0 –ip route 10.3.0.0 255.255.0.0 10.2.0.1 Can add optional administrative distance param Use show ip route to view routing table

5. Copyright © 2005 University of Bolton Step-by-step 1.Determine all desired prefixes, masks, and addresses 2.Enter global configuration mode. 3.Type the ip route command with a prefix and mask followed by the corresponding address from Step 1. The administrative distance is optional. 4.Repeat Step 3 for all the destination networks in Step 5.Exit global configuration mode. 6.copy running-config startup-config

6. Copyright © 2005 University of Bolton Default Route Impossible to write for every combination when using static routes Typically add a default entry to send packets that don't match any rules to a default gateway router ip route 0.0.0.0 0.0.0.0 gateway

7. Copyright © 2005 University of Bolton Testing show ip route –displays routing table show running-config –displays config file as entered Use ping command to test connectivity Use traceroute command to determine where mis-configuration occurs

8. Dynamic Routing

9. Copyright © 2005 University of Bolton Routing Protocols Used by routers to share information about connected networks Examples of routing protocols are as follows: –Routing Information Protocol (RIP) –Interior Gateway Routing Protocol (IGRP) –Enhanced Interior Gateway Routing Protocol (EIGRP) –Open Shortest Path First (OSPF)

10. Copyright © 2005 University of Bolton Autonomous Systems (AS) "An AS is a collection of networks under a common administration that share a common routing strategy. " Viewed by outside world as single entity Each AS assigned unique 16-bit number by authority such as ARIN

11. Copyright © 2005 University of Bolton Goal of routing protocols Build routing table using data learned from neighbours Best routes are placed in routing table Table recalculated when changes occur When all routers share optimum config – network is said to be converged

12. Copyright © 2005 University of Bolton Protocol classes Distance Vector –Determines direction and distance (vector) to other networks Link-state –Each router builds a copy of network topology –Reflects network conditions

13. Copyright © 2005 University of Bolton Distance Vector overview Routers receive copies of neighbours' routing tables Links to connected networks given metric such as hop count Add details to own tables with neighbour as gateway (updating routing metric) Details spread through networks as learned routes are passed on Routers choose best route to distant networks

14. Copyright © 2005 University of Bolton Link-state overview Each router builds a detailed topology database of remote routers and their networks Builds a tree-structure with self as route Uses SPF algorithm (Dijkstra's) to calculate best routes Link State Advertisements update neighbours of changes and recalculate topology database

15. Copyright © 2005 University of Bolton Comparison Link-state algorithms generally require –greater CPU power than Distance Vector –more memory to maintain topology –greater initial bandwidth for convergence Once stable, minimal overhead is required to maintain

16. Routing Protocols Overview

17. Copyright © 2005 University of Bolton Path Determination Path Determination Function –Uses layer 3 addressing –Routing table to determine outbound interface Switching Function –Packets forwarded to appropriate interface –Layer 2 encapsulation appropriate for next data link

18. Copyright © 2005 University of Bolton Routing Configuration Global task to specify routing protocol to use GAD(config)# router rip Routing configuration mode used to... –specify networks GAD(config-router)# network 192.168.77.0 –Configure protocol settings such as update intervals and timeouts

19. Copyright © 2005 University of Bolton RIP RIP a basic routing protocol for small networks. Its key characteristics include the following: –It is a distance vector routing protocol. –Hop count is used as the metric for path selection. –If the hop count is greater than 15, the packet is discarded. –Routing updates are broadcast every 30 seconds, by default.

20. Copyright © 2005 University of Bolton IGRP IGRP is a proprietary protocol developed by Cisco. Some of the IGRP key design characteristics are as follows: –It is a distance vector routing protocol. –Bandwidth, load, delay and reliability are used to create a composite metric. –Routing updates are broadcast every 90 seconds, by default. IGRP is being phased out by Cisco

21. Copyright © 2005 University of Bolton OSPF OSPF is a nonproprietary link-state routing protocol. –It is a link-state routing protocol. –It is an open standard routing protocol described in RFC 2328. –The SPF algorithm is used to calculate the lowest cost to a destination. –Routing updates are flooded as topology changes occur.

22. Copyright © 2005 University of Bolton EIGRP EIGRP is a Cisco proprietary enhanced distance vector routing protocol. Key characteristics: –It uses unequal cost load balancing. –It uses a combination of distance vector and link-state features. –It uses Diffused Update Algorithm (DUAL) to calculate the shortest path. –Routing updates are multicast using 224.0.0.10 triggered by topology changes.

23. Copyright © 2005 University of Bolton BGP Border Gateway Protocol (BGP) is an exterior routing protocol. The key characteristics of BGP are as follows: –It is a distance vector exterior routing protocol. –It is used between ISPs or ISPs and clients. –It is used to route Internet traffic between autonomous systems.

24. Copyright © 2005 University of Bolton IGP vs EGP Interior Gateway protocol within AS Exterior Gateway protocol between AS EGPs require: –A list of neighbor routers with which to exchange routing information –A list of networks to advertise as directly reachable –The autonomous system number of the local router