Dynamic routing protocols (CCNA)

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

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

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
 RIP
 OSPF
 EIGRP

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.

Dynamic routing protocols (CCNA)

Dynamic routing protocols (CCNA)

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