Dynamic routing
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This document discusses routing concepts and types of routing protocols. It defines routing as moving information across a network from source to destination based on IP address. There are static and dynamic routing protocols, with dynamic routing allowing routers to automatically learn and update routing tables in response to network changes. Interior gateway protocols like OSPF and IS-IS are used within autonomous systems, while exterior gateway protocols like BGP route between autonomous systems. Classful protocols do not include subnet masks while classless protocols do, allowing for variable length subnet masking. Administrative distance numbers and metrics are used to determine the best path when multiple routes exist. Distance vector protocols use the Bellman-Ford algorithm while link state protocols have each node build a connectivity map to calculate best
Dynamic routing
- 1. What is a routing Routingisthe act of movinginformationacrossaninternetworkfromasource to a destination basedon the destinationIPaddress. Typesof IP routing 1) Static 2) Default 3) dynamic Dynamic routing Dynamic routingis a processinwhich use routingprotocol that allow router to dynamicallylearn informationabout remote networks and automatically add this information to their own routing tables. Advantage:- ■Administrator has less work in maintaining the configuration when adding or deleting networks. ■Protocols automatically react to the topology changes. ■More scalable; growing the network usually does not present a problem. Disadvantage:- ■Router resources are used (CPU cycles, memory, and link bandwidth). ■More administrator knowledge is required for configuration, verification, and troubleshooting. Advantages of static routing -It can backup multiple interfaces/networks on a router -Minimal CPU processing -Easier for administrator to understand -Easy to configure -No extra resources are needed -More secure Disadvantages of static routing -Network changes require manual reconfiguration -Configuration and maintenance is time-consuming -Does not scale well in large topologies -Configuration is error-prone, especially in large networks Dynamic routing broken into two types IGP and EGP An autonomous system (AS)—otherwise known as a routing domain—is a collection of Routers which operate under a common administration. Typical examples are a company’s internal network and an ISP’s network. Because the Internet is based on the autonomous system concept, two types of routing protocols are required: interior and exterior routing protocols. These protocols are ■Interior gateway protocols(IGP): Used for intra-autonomous system routing, that is, routing inside an autonomous system (RIP, IGRP, EIGRP, ISIS, OSPF) ■Exteriorgateway protocols(EGP): Used for inter-autonomous system routing, that is, routing between autonomous systems (BGP)
- 2. Classfuland Classless RoutingProtocols Classful routingprotocol: -theydo not send subnet mask information in routing updates.so don’t support VLSM. (RIP, IGRP) Classless routing protocol: - Classless routing protocols include the subnet mask with the network address in routing updates. Support VLSM (RIPv2, EIGRP,OSPF, ISIS, BGP) Contiguous network When two subnetted network are connected with the network of same subnet on two or more router. Discontigous network When two subnetted network are separated by different network with two or more router Summarization Summarization, also called route aggregation, allows routing protocols to advertise many networks as one address. The purpose of this is to reduce the size of routing tables on routers to save memory. Administrative distance number AD number is use for path selection, when single route learn from two different routing domain Its 8 bits value (0-255), lowest AD number preferred than higher. Note:- it’s a locally significant value. Routing protocol AD number Connected 0 static 1 summary EIGRP 5 External BGP 20 Internal EIGRP 90 IGRP 100 OSPF 110 ISIS 115 RIP 120 EGP 140 External EIGRP 170 Internal BGP 200 No traffic 255 Metrics A metric is a value that routing protocols use to measure path to a destination. Different routing protocols use diff way to calculate the best path. If multiple paths have the same metric, a maximum 16 path can be installing Note:- before cisco ios release 12.3(2)T , the maximum number of parallel routes supported by ip routing protocols was 6 ; in cisco ios release 12.3(2)T that maximum was changed to 16.
- 3. Distance Vectorand Link-State Routing Protocols Distance vector:- itbasedonbellman-fordalgorithmforthe best-pathdetermination. The algorithm doesnotallowa routerto knowthe exact topologyof aninternetwork.The routeronly knows the routing information received from its neighbors.(so its called route by rumor) Link state:- The basic concept of link-state routing is that every node build a map of the connectivity to the network, in the form of a graph, showing which nodes are connected to which other nodes. Each node then independently calculates the next best logical path from it to every possible destination in the network. The collection of best paths will then form the node's routing table.