1. Routing protocols

2. Static Routing Routes to destinations are set up manually Route may be up or down but static routes will remain in the routing tables and traffic would still be sent towards the route Not suitable for large networks Also known as Non-adaptive routing Static/Default route entries

3. Dynamic Routing Routes are learnt via an internal or external routing protocols Network reachability is dependent on the existence and state of the network Routing decisions change to reflect the changes in topology Also known as Adaptive routing

4. Path Determination AB C 192.168.1.0 192.168.7.0 192.168.6.0 192.168.5.0 192.168.2.0 192.168.3.0 192.168.4.0 Router-A Network Next Hop Router 192.168.1.0Direct 192.168.2.0Direct 192.168.3.0Direct 192.168.4.0B,C 192.168.5.0B,C 192.168.6.0B,C 192.168.7.0B,C Networks192.168.4.0 to 192.168.7.0 can be reached via either router B or C, which path is preferable? Metrics are needed to rank the alternatives.

5. Metrics Hop Count Bandwidth Load Delay Reliability

6. Autonomous System Definition An autonomous system is an internetwork under a common administration AS numbers are assigned in blocks by the Internet Assigned Numbers Authority (IANA) to regional Internet registries (RIRs). The appropriate RIR then assigns AS numbers to entities within its designated area AS No: 16 bits and 32 bits with Public and Private ranges like in IPv4 http://en.wikipedia.org/wiki/Autonomous_System_(Internet)

7. Autonomous systems

8. Popular routing protocols

9. Link State Link state protocols, such as IS-IS and OSPF, rely on each router in the network to advertise the state of each of their links to every other router within the local routing domain. In distance vector routing, each node shares the knowledge about the entire AS with its immediate neighbors periodically. This result is a complete network topology map, called a shortest path tree, compiled by each router in the network. It uses an algorithm, called the shortest path first algorithm, to build a tree with itself as the center of that tree.

10. Distance Vector Routers running distance vector algorithms advertise the vector (path) and distance (metric) for each destination reachable within the network to adjacent (directly connected) peers. Once the best path is determined, these best paths are advertised to each directly connected adjacent router, not every one as in Link State Two common algorithms used for determining the best path are Bellman-Ford, which is used by the Routing Information Protocol (RIP and RIPv2), and the Diffusing Update Algorithm (DUAL), used by the Enhanced Interior Gateway Protocol (EIGRP).

11. Path Vector A path vector protocol does not rely on the cost of reaching a given destination to determine whether each path available is loop free or not. Instead, path vector protocols rely on analysis of the path to reach the destination to learn if it is loop free or not. This algorithm used is Bellman–Ford routing algorithms to avoid "Count to Infinity" problems. http://www.informit.com/articles/article.aspx?p=331613&seqNum=2

12. Routing Updates After exchanging 2 periodic updates, the network is converged. 10.1.2.0 10.1.1.010.1.3.010.1.4.0.2.1.2.1.2 ABC 10.1.4.0 10.1.2.2 210.1.1.0 10.1.3.1 2 10.1.3.0 10.1.2.2 1 10.1.1.0 10.1.2.1 1 10.1.4.0 10.1.3.2 1 10.1.2.0 10.1.3.1 1 NW VIA HOP 10.1.1.0 ---------- 0 10.1.2.0 ---------- 0 NW VIA HOP 10.1.2.0 ---------- 0 10.1.3.0 ---------- 0 NW VIA HOP 10.1.3.0 ---------- 0 10.1.4.0 ---------- 0 Routing Table-A Routing Table-B Routing Table-C

13. Fully adjacent router network R A -R B -4 R A -R C -10 R A -R D -5 R D -R A -5 R D -R B -3 R D -R C -2 R C -R A -10 R C -R D -2 R B -R A -4 R B -R D -3 A C B D tntn R C -R A -10 R C -R D -2 R D -R A -5 R D -R B -3 R D -R C -2 R B -R A -4 R B -R D -3 R A -R B -4 R A -R C -10 R A -R D -5 t n+1 R C -R A -10 R C -R D -2 R B -R A -4 R B -R D -3 t n+2 AB CD 44 105 22 53 3

14. Shortest Path Tree of Router-A AB CD 44 105 22 53 3 AB CD 4 5 2

15. PATH VECTOR ROUTING Path vector routing is similar to distance vector routing. There is at least one node, called the speaker node, in each AS that creates a routing table and advertises it to speaker nodes in the neighboring ASs..

16. Initial routing tables in path vector routing

17. Stabilized tables for four autonomous systems

18. Administrative Distances Diversity of metrics poses problems in routers running more than one routing protocol. Router may learn a route to the same destination from each of the protocols Administrative distances are the route sources to determine most preferred source Administrative distance is a measure of believability

19. Administrative Distances The administrative distance of various protocols is as below: Connected Interface - 0 Static Route - 1 OSPF - 110 RIP - 120 Unknown - 255 The lower the administrative distance, the more believable the protocol

20. Packet Received Received ARP Reply Send ICMP error message Discard original Packet Header & Checksum Valid Route Found Route table lookup on Dest. Add. YES NO Decrement TTL; TTL>=0 YES NO YES NO If route available, search MAC in ARP cache Default route available NO YES Send ARP request and wait for a response Build new packet with MAC address and route through port found in routing table MAC Address Found YES NO Received ARP reply, insert MAC and IP address into ARP table YES NO Flow Chart of a Packet