DYNAMIC ROUTING PROTOCOLS

PRESENTED BY-:VARINDER SINGH WALIA

DYNAMIC ROUTING PROTOCOLS

Dynamic routing protocols help the network administrator overcome the time-consuming and exacting process of configuring and maintaining static routes.

The purpose of a dynamic routing protocol is to:

Discover remote networks Maintaining up-to-date routing information Choosing the best path to destination networks Ability to find a new best path if the current path is no longer available

CLASSIFYING ROUTING PROTOCOLS

Interior Gateway Routing Protocols (IGP)

-Used for routing inside an autonomous system & used to route within the individual networks themselves.-Examples: RIP, EIGRP, OSPF

Exterior Routing Protocols (EGP)-Used for routing between autonomous systems-Example: BGPv4

DYNAMIC ROUTING PROTOCOLS

CLASSIFYING ROUTING PROTOCOLS

Classful routing protocols

Do NOT send subnet mask in routing updates

Classless routing protocols

Do send subnet mask in routing updates.

ROUTING PROTOCOLS METRICS

Metric A value used by a routing protocol to determine which routes are better than others.

Metrics used in IP routing protocols:

-Bandwidth-Cost-Delay-Hop count-Load-Reliability

AD VALUE FOR ROUTING PROTOCOLS it is a numeric value that specifies the preference of a particular route

INTERIOR ROUTING PROTOCOLS

RIPOSPFEIGRP

ROUTING INFORMATION PROTOCOL

The Routing Information Protocol (RIP) is an intradomain routing protocol used inside an autonomous system. It is a very simple protocol based on distance vector routing.

A metric in RIP is called a hop count; distance; defined as the number of links (networks) that have to be used to reach the destination.

Distance vector algorithm.Included in BSD-UNIX Distribution in 1982

COMMAND USED

Router (config)# router rip Router (config-router)# network_required network

IP

RIP CHARACTERISTICS

Distance vector routing protocol. Uses hop count as a path selection

metric. Three types of timers. Multiple stability features.

Hop Count -- Fifteen Hop Limit

- Hop count is the sum of all the legs in a route.

-After 15 hops, the packet is discarded

RIP TIMERS

Timers in RIP

Periodic timer : controlling the advertisements of regular update messages

expiration timer : governing the validity of a route

the garbage collection timer : advertising the failure of a route

RIPv2 RIPv2 is an extends RIPv1:

Subnet masks are carried in the route information

Authentication of routing messages Route information carries next-hop address Exploites IP multicasting

Extensions of RIPv2 are carried in unused fields of RIPv1 messages

COMMAND USED

Router (config)# router rip Router (config)# ver 2 Router (config-router)# network_required network

IP

RIP ADVANTAGES

Advantages Simplicity ; little to no configuration, just

start routed up Passive version for hosts

If a host wants to just listen and update its routing table

RIP Problems

RIP takes a long time to stabilize Even for a small network, it takes several

minutes until the routing tables have settled after a change

RIP has all the problems of distance vector algorithms, e.g., count-to-Infinity

RIP uses split horizon to avoid count-to-infinity

The maximum path in RIP is 15 hops

OSPF (Open Shortest Path First)

The Open Shortest Path First (OSPF) protocol is an intradomain routing protocol based on link state routing. Its domain is also an autonomous system

Dividing an AS(autonomous system) into areas to handle routing efficiently and in a

timely manner

Functional Requirements of OSPF

Faster Convergence and less consumption of network resources

A more descriptive routing metric configurable value ranges between 1 and 65,535 no restriction on network diameters

Equal-cost multipath a way to do load balancing

Functional Requirements(contd.)

Routing Hierarchy support large routing domains

Separate internal and external routes Support of flexible subnetting

schemes route to arbitrary [address,mask]

combinations using VLSMs Security Type of Service Routing

OSPF (cont’d) Areas

Is a collection of networks, hosts, and routers in AS AS can be divided into many different areas. All networks inside an area must be connected. Routers inside an area flood the area with routing

information. Area Border Router

Summarizes the information about the area and sends it to other areas

Backbone All of the areas inside an AS must be connected to the

backbone Serving as a primary area Consisting of backbone routers Back bone routers can be an area border router

OSPF (cont’d) Metric

OSPF protocol allows the administrator to assign a cost, called the metricc, to each route

Based on a type of service (minimum delay, maximum throughput, and so on)

A router can have multiple routing tables, each based on a different type of service.

Link State Routing OSPF uses Link State Routing to update the routing

tables in an area Each router shares its knowledge about its

neighborhood with every router in the area.

OSPF (cont’d) Types of Links

In OSPF terminology, a connection is called a link.

OSPF (cont’d)

Point-to-point Link Routers are represented by nodes and

the link is represented by a bidirectional edge connecting the nodes.

Each router has only one neighbor at the other side of the link.

OSPF (cont’d)• Tranisent network: is a network with several routers

attached to transient Link .

(network)

OSPF (cont’d) Stub Link

is a network that is connected to only one router

is a special case of transient network The link is only one-directional, from the

router to the network.

OSPF (cont’d)

Virtual Link

When the link between two routers is broken, the administration may create a virtual link between them using a longer path

Graphical Representation An internet with 7 networks and 6 routers

SYNTAX

Router (config )# router ospf_ PID(range 1-65535) Router (config –router)# network_requires network

IP_ wildcard mask_area_any value(range 0-4294967295)

EIGRP A classless version of IGRP. EIGRP includes several features that are not

commonly found in other distance vector routing protocols like RIP (RIPv1 and RIPv2) and IGRP.

These features include: Reliable Transport Protocol (RTP) Bounded Updates Diffusing Update Algorithm (DUAL) Establishing Adjacencies Neighbor and Topology Tables

Although EIGRP may act like a link-state routing protocol, it is still a distance vector routing protocol.

Path Determination (1) Traditional distance vector routing protocols such

as RIP and IGRP keep track of only the preferred routes; the best path to a destination network.

If the route becomes unavailable, the router waits for another routing update with a path to this remote network.

EIGRP's DUAL maintains a topology table separate from the routing table. including both the best path to a destination network and

any backup paths that DUAL has determined to be loop-free.

Loop-free means that the neighbor does not have a route to the destination network that passes through this router.

Path Determination (2) If a route becomes unavailable, DUAL will

search its topology table for a valid backup path.

If one exists, that route is immediately entered into the routing table.

If one does not exist, DUAL performs a network discovery process to see if there happens to be a backup path that did not meet the requirement of the feasibility condition.

SYNTAX :

Router (config)# router eigrp_PROCESS ID ( ) Router (config-router)# network _ required

network IP

EXTERIOR ROUTING PROTOCOL

BORDER GATEWAY PROTOCOL

Routing protocols used to route information between multiple autonomous systems

BGP (Border Gateway Protocol) is a protocol for exchanging routing information between gateway hosts (each with its own router) in a network of autonomous systems. BGP is often the protocol used between gateway hosts on the Internet. The routing table contains a list of known routers, the addresses they can reach, and a cost metric associated with the path to each router so that the best available route is chosen.

SYNTAX:

Router (config)#router bgp_PID1 Router (config)#Network directly connect Router (config –router)# neighbor_ip of end

point_remote-as_PID2 NOTE 1: Before applying this command apply Dynamic

routing on each router NOTE 2: Each router has different Process ID NOTE 3:Do not write directly attached IP of network. All

except directly attached IP will be treated as neighbor NOTE 4: PID will be of current router only.