1. Routers are networking devices that connect different networks and forward data packets between them. They maintain routing tables to determine the best paths between networks. 2. The main functions of routers are packet forwarding, packet switching, and packet filtering. Routers examine packet headers to determine the best path using routing tables and switch packets between interfaces. 3. Common router operating systems are Cisco IOS and Juniper JUNOS. Cisco IOS is customized for Cisco devices and provides tools for management, memory allocation, and file storage. Juniper JUNOS offers a modular architecture and policy-based traffic controls.

1. PRESENTED BY-
AMITESH GAURAV
SHANU SONI
ASHOK RAJAK

2. ROUTERS AND ROUTING

3. What is computer network?
A network is group of computers interconnected with each other to exchange
information or resource.
A computer network is collection of interconnected autonomous computers
interconnected in a single technology.
Two computers are said to interconnected with each other if they share some
information between them.

4. A world without networks and routing
 No connection between offices,
people and applications
 Worldwide chaos because of the lack
of centralized configurations and
support
 Limited possibilities of
communications on vocal and visual
levels
 No further technical progress
achievements

5. Advantages of having computer network
 Increased communication capabilities
 File sharing: Network offer quick and easy way to share files directly at a rapid speed
thus saving time and integrity of files.
 Resource sharing : All computers in a network can share resources like printer, scanner,
modem, fax machines, hard disk.
 You can connect all the computers which are connected through a network to the
internet by using a single line.
 Internet connection sharing - Using a home network, multiple family members can
access the Internet simultaneously without having to pay an ISP for multiple accounts.

6. INTRODUCTION TO ROUTER

7. WHAT IS ROUTER ?
A router is an electronic device that interconnects two
or more computer networks
A router is a device that forwards data packets along
networks
Can connect different network segments, whether they
are in the same building or even on the opposite side
of the globe .

8. History of the Router
Interface Message Processor
The IMP or Interface Message Processor was the first device used as a router. In April
1967, a computer scientist by the name of Wesley A. Clark suggested the idea to
incorporate IMP to the ARPANET (Advanced Research Projects Agency Network) during
a design session with Lawrence Roberts, chief scientist of ARPANET.
Multi-Protocol Router
An American engineer named William Yeager created the first multi-protocol router at
Stanford University. The router supported two or more protocols, like Internet Protocol
version 4 (IPv4) and IPv6.
Cisco
•Len Bosack and Sandy Lerner, former members of the computer operation staff at
Stanford University, founded Cisco, a U.S. corporation. The first Cisco product
developed was based on Yeager's multi-protocol router.

9. FUNCTION OF ROUTER
Router has generally three main functions:-
 Packet Forwarding
 Packet switching
 Packet filtering

10. Router maintains a routing table for all possible networks those can be reached.
In the routing table, a router maintains, subnet, Gateway, forwarding interface,
timing etc of the destination network. If multiple paths exist to reach the
destination network, only best path is maintained in the routing table.
Once any packet is received, it checks the destination IP network in the routing
table. If destination network is available in routing table, It forwards the packet
otherwise it drops.
PACKET FORWARDING:

11. PACKET SWITCHING :
To move packets from one interface to another to get a packet to its
destination.
PACKET FILTERING:
Packet filtering is such like firewall. By which you can define which network
can be entered and which network can be dropped. In easy word, It filters the
packet on the basis of IP address, subnet, port no and protocols.

12. Routers examine a packet’s destination IP address and determine the best path by
enlisting the aid of a routing table .
The Best Path

13. Routers Operates in Network Layer of OSI Model
OSI (Open Systems Interconnection) is
reference model for how applications can
communicate over a network

14. The Network Layer
 Layer 3 on the OSI reference model
 The layer at which routing occurs
 The network layer is responsible for packet
forwarding including routing through intermediate
routers.
 Responds to service requests from the transport layer
and issues service requests to the data link layer.

15. Difference Between Router and Switch
 Switches
• Examine the data packet for the
destination address
 Routers
• Examine and alter the data packets
Perform protocol conversion
“Switches create a network and Routers connect networks”

16. Which Routers to buy ?
Many companies are manufacturing Router :
 Cisco
 Netgear
 Nortel
 Multicom
 Cyclades
 Juniper
 D Link
 Linksys
 3Com
But Cisco is having monopoly in the market of Routers

17. Cisco’s Market Share
CISCO 60%
40%
D-Link
3 Com
Nortel
Cygnus
Etc..

18. Cisco’s Hierarchical Design Model
Cisco divided the Router into 3 Layers
 Access Layer Router
 Distribution Layer Router
 Core Layer Router

19. The benefits of the Cisco hierarchical model
• High Performance: You can design high performance networks, where only certain layers
are susceptible to congestion.
• Efficient management & troubleshooting: Allows you to efficiently organize network
management and isolate causes of network trouble.
• Policy creation: You can easily create policies and specify filters and rules.
• Scalability: You can grow the network easily by dividing your network into functional
areas.
• Behavior prediction: When planning or managing a network, the model allows you
determine what will happen to the network when new stresses are placed on it.

20. Access Layer Router
•Routers which are used by the Small Organization and
are also known as Desktop or Company Layer Routers.
Router Series : 800, 1000, 1600, 1700, 2500
Cisco 1700 Cisco 1760Cisco 800

21. •Routers which are used by the ISPs and are also
known as ISP Layer Routers
Router Series : 2600, 3200, 3600, 3700
Distribution Layer Router
Cisco 2600XM/2691
Cisco 3700Cisco 3600

22. •Routers which are used by the Global ISPs and are also known
as Backbone Routers
Router Series : 6400, 7200, 7300, 7400, 7500, 7600,
10000, 12000
Core Layer Router
Cisco 7000

23. MODULAR
FIXED

27. ROUTER
IOS

28. Router operating system
The router operating system is a piece of software responsible for managing the router
resources by controlling and allocating memory, prioritizing system requests and
processes, controlling I/O devices and managing file systems.
The most two famous router operating systems:-
 Cisco IOS
 Juniper JUNOS

29. What is IOS?
Operating System of all Cisco Devices
A derivative of BSD UNIX
Custom built by Cisco for each platform
Features available in different versions (for a price!)
GUI’s available, but 90%+ of users still prefer command-line configuration.
IOS is designed to be hardware independent.

30. Cisco IOS
Cisco IOS is a monolithic OS which means it runs as a single operation with all processes
sharing the same memory space.
The Cisco IOS contains the instruction sets needed to configure, maintain, and run a
Cisco router successfully in any environment.

31. Advantage of Cisco IOS
 Robust operating system
 Cisco IOS is a very efficiently assembled package of commands and functions for
managing routers.
 The IOS provides tools for file storage, memory management
 Cisco IOS is extremely user friendly and easy to learn

32. Juniper JUNOS
JUNOS OS is a reliable, high-performance network operating system for routing,
switching, and security.
It reduces the time necessary to deploy new services and decreases network operation
costs. JUNOS OS offers secure programming interfaces and the JUNOS SDK for developing
applications that can unlock more value from the network.

33. Advantage of Juniper JUNOS
 One operating system reduces time and effort to plan, deploy, and operate network
infrastructure.
 Modular software architecture provides highly available and scalable software that
keeps up with changing needs.
 Simple routing policy management supports fine-grained network traffic controls.
 Separate control and forwarding planes increase reliability and security.

34. Router Components
This section discusses the hardware elements of the router:
 CPU
ROM
Flash memory
NVRAM
RAM/DRAM

35. CPU
 The CPU executes operating system instructions, such as
system initialization, routing functions, and switching
functions.
 50 MHz CPUs are generally used for small offices & homes.

36. Read-only memory (ROM)
 Loads the bootstrap program that initializes the router’s basic
hardware components
 Not modified during normal operations, but it can be upgraded with
special plug-in chips
 The content of ROM is maintained even when the router is rebooted
 The ROM monitor firmware runs when the router is turned on or
rebooted
ROM

37. Flash memory
 A type of erasable, programmable, read-only memory (EPROM)
 The content of flash memory is maintained even when the router is rebooted Flash
memory
 Contains the working copy of the current Cisco IOS
 Is the component that initializes the IOS for normal router operations
Flash Memory

38. Naccess memory (NVRAM) onvolatile random
 A special type of RAM that is not cleared when the router is rebooted
 The startup configuration file for the router is stored in NVRAM by default
o This is the first file created by the person who sets up the router
 The Cisco IOS uses the configuration file in NVRAM during the router boot process
NVRAM

39. RAM/DRAM
Random access memory (RAM)
 Also known as dynamic random access memory (DRAM)
 A volatile hardware component
 Its information is not maintained in the event of a router reboot
 Changes to the router’s running configuration take place in RAM/DRAM

41. Router Interface
refers to a physical connector on the router whose main purpose is to receive and
forward packets.

42. Router interfaces can be divided into two major groups:
o LAN interfaces
o WAN interfaces
Router Interface(Cont’d…)

43.  A LAN is connecting two or more computers to form a cable network between
them.
 This can mean all in the same office or building, or in a group of nearby buildings
LOCAL AREA NETWORK

44. WIDE AREA NETWORK
 A wide area network is one that covers a much bigger region than a local area
network
 The WAN port takes in information from the outside network or the Internet.

45. Router Boot Sequence

46. Router Boot Sequence(Cont’d…)
The sequence of events that occurs during the powerup (also known as the booting of a
router) is important to understand. When power initially is applied to a router, the
following events occur in the order shown:-
• Power-on self-test (POST)— This event is a series of hardware tests to verify
that all the router's components are functional. During this test, the router also
determines what hardware is present. POST executes from microcode resident
in the system ROM.
• Load and run bootstrap code— Bootstrap code is used to perform
subsequent events, such as finding the Cisco IOS Software, loading it, and then
running it. After Cisco IOS Software is loaded and running, the bootstrap code is
not used until the next time the router is reloaded or power-cycled.

47. Router Boot Sequence(Cont’d…)
Finding Cisco IOS Software— The bootstrap code determines where Cisco IOS Software
to be run is located. The Flash memory is the normal place where a Cisco IOS Software
image is found. The configuration register and configuration file in NVRAM help
determine where the Cisco IOS Software images are and what image file should be used.
Load Cisco IOS Software— After the bootstrap code has found the proper image, it loads
that image into RAM and starts Cisco IOS Software running. Some routers (such as the
2500 series) do not load the Cisco IOS Software image into RAM but execute it directly
from Flash memory.

48. Router Boot Sequence(Cont’d…)
•Find the configuration— The default is to look in NVRAM for a valid configuration.
A parameter can be set to have the router attempt to locate a configuration file from
another location, such as a TFTP server.
•Load the configuration— The desired configuration for the router is loaded and
executed. If no configuration exists or the configuration is being ignored, the router
will enter the setup utility or attempt an autoinstall.Autoinstall will be attempted if a
router is connected to a functioning serial link and can resolve an address through a
process of the Serial Line Address Resolution Protocol (SLARP).
•Run— The router now is running the configured Cisco IOS Software.

49. ROUTING
PROTOCOL

50. Routing Protocols
Protocols used by routers to make path determination choices and to share those
choices with other routers

51. MINIMUM CONDITION FOR ROUTE PACKETS
Destination address
Neighbor routers from which it can learn about remote networks
Possible routes to all remote networks
The best route to each remote network
How to maintain and verify routing information

52. Types Of Routing
 Static routing
 Dynamic routing

53.  Static Routing-Static routing is the process of an
administrator manually adding routes in each router’s routing table.
ADVANTAGE
• No overhead on the router CPU
• No bandwidth usage between
routers
• Security (because the
administrator only allows routing
to certain networks)
DISADVANTAGE
• Static routes require extensive
planning and have high
management overhead.
• Static routing does not scale
well in large networks.
• For n number of router ,You
have to configure n*n Routers.

54.  Dynamic Routing-Dynamic routing, the routing protocol operating on
the router is responsible for the creation, maintenance and updating of the
dynamic routing table itself.
ADVANTAGE
• Simpler to configure on larger
networks
• Will dynamically choose a
different (or better) route if a link
goes down
• Ability to load balance between
multiple links
DISADVANTAGE
• Updates are shared between
routers, thus consuming bandwidth
• Routing protocols put additional
load on router CPU/RAM
• The choice of the “best route” is in
the hands of the routing protocol.

55. Routing Protocol Goals
 Optimal path selection
 Loop-free routing
 Fast convergence
 Limited design
 Administration
 Minimize update traffic
 Handle address limitations
 Support hierarchical
 Topology
 Incorporate rapid
 Convergence
 Easy to configure
 Adapts to changes
 Easily and quickly
 Does not create a lot of traffic
 Scales to a large size
 Compatible with existing hosts and
routers
 Supports variable length
 Subnet masks and• Supports policy
routing

56. Common fields of a Routing table
 Mask. This field defines the mask applied for the entry.
 Network address: This field defines the network address to which the packet is
finally delivered. In the case of host-specific routing, this field defines the address of
the destination host.
 Next-hop address: This field defines the address of the next-hop router to which
the packet is delivered.

57. Common fields of a Routing table(continued)
 Interface: This field shows the name of the interface.
 Flags: This field defines up to five flags. Flags are on/off switches that signify
either presence or absence. The five flags are U (up), G (gateway), H (host-specific),
D (added by redirection), and M (modified by redirection).
 Reference count: This field gives the number of users of this route at the moment.
For example, if five people at the same time are connecting to the same host from this
router, the value of this column is 5.
 Use: This field shows the number of packets transmitted through this router for the
corresponding destination.

58. There are two basic routing algorithms found on the Internet.
Distance Vector Routing
 Each node knows the distance (=cost) to its directly connected neighbors
 A node sends periodically a list of routing updates to its neighbors.
 If all nodes update their distances, the routing tables eventually converge
 New nodes advertise themselves to their neighbors

59. Link State Routing
 Each node knows the distance to its neighbors
 The distance information (=link state) is broadcast to all nodes in the network
 Each node calculates the routing tables independently

60. DIFFERENCES

61. Distance Vector
• Routing Information Protocol (RIP)
• Interior Gateway Routing Protocol
(IGRP)
Link State
• Intermediate System - Intermediate
System (IS-IS)
• Open Shortest Path First (OSPF)
Routing Algorithms(Continued)

62. Routing Information Protocol
-> Routing Information Protocol (RIP)
 The easiest Interior Gateway Protocol to configure is RIPv1
 A distance-vector routing protocol that broadcasts entire routing tables to
neighbors every 30 seconds
 RIP uses hop count as its sole metric
->RIP has a maximum hop count of 15
 As a result, RIP does not work in large internetworks
 RIP is capable of load balancing
 RIP is susceptible to all the problems normally associated with distance-vector routing
protocols

63. Due to the deficiencies of the original RIP specification, RIP version 2 (RIPv2) was
developed in 1993

64. RIP DISADVANTAGE
 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
 The maximum path in RIP is 15 hops

65. Interior Gateway Routing Protocol (IGRP)
 Interior Gateway Routing Protocol is a distance vector routing protocol
developed by Cisco systems for routing multiple protocols across small and
medium sized Cisco networks.
 This contrasts with IP RIP and IPX RIP, which are designed for multi-vendor
networks.
 IGRP was for very versatile for clients running many different protocols

66. IGRP Characteristics
• Distance Vector
• Routing Table Advertisements Every 90 Seconds
• Metric: Bandwidth, Delay, Reliability, Load, MTU Size
• Hop Count: 100
• Fixed Length Subnet Masks
• Summarization on Network Class Address
• Update Timer: 90 seconds
• Invalid Timer: 270 seconds
• HoldDown Timer: 280 seconds
• Metric Calculation = destination path minimum BW *
delay(usec)

67. Enhanced Interior Gateway Routing Protocol (EIGRP)
Enhanced Interior Gateway Routing Protocol is a hybrid routing protocol
developed by Cisco systems
It has characteristics of both distance vector routing protocols and link state
routing protocols
EIGRP is faster since it uses an algorithm called dual update algorithm, which
is run when a router detects that a particular route is unavailable.

68. EIGRP Characteristics
• Advanced Distance Vector
• Routing Advertisements: Partial When Route Changes Occur
• Metrics: Bandwidth, Delay, Reliability, Load, MTU Size
• Hop Count: 255
• Variable Length Subnet Masks
• Summarization on Network Class Address or Subnet Boundary
• Load Balancing Across 6 Equal or Unequal Cost Paths (IOS 11.0)
• Hello Timer: 5 seconds on Ethernet / 60 seconds on Non-Broadcast
• Holddown Timer: 15 seconds on Ethernet / 180 seconds on Non-Broadcast
• Metric Calculation = destination path minimum BW * delay (msec) * 256

69. Open Shortest Path First (OSPF)
 A routing protocol developed for Internet Protocol networks by the Interior Gateway
Protocol (IGP)
 Based on the Dijkstra’s Algorithm
 Serving large, heterogeneous internetworks
It has Versions
 OSPF Version 1 (1988)
 OSPF Version 2 (1998) Supported IPv4
 OSPF Version 3 (2008) Supported IPv6

70. When to Use OSPF
• Large hierarchical networks
• Complex networks, except…
Topology restrictive
Additional network design
• VLSM
• Fast convergence
• Multivendor

71. OSPF Characteristics
• Link State
• Routes IP
• Routing Advertisements: Partial When Route Changes Occur
• Metric: Composite Cost of Links to Destination (100 Mbps/interface speed)
• Hop Count: None (Limited by Network)
• Variable Length Subnet Masks
• Summarization on Network Class Address or Subnet Boundary
• Load Balancing Across 4 Equal Cost Paths
• Router Types: Internal, Backbone, ABR, ASBR
• Area Types: Backbone, Stubby, Not-So-Stubby, Totally Stubby
• LSA Types: Intra-Area (1,2) Inter-Area (3,4), External (5,7)
• Hello Timer Interval: (10 seconds for Ethernet / 30 seconds for Non-Broadcast)
• Dead Timer Interval: 40 sec. for Ethernet / 120 sec. for Non-Broadcast
• LSA Multicast Address: 224.0.0.5 and 224.0.0.6 (DR/BDR) Don't Filter!
• Interface Types: Point to Point, Broadcast, Non-Broadcast, Point to Multipoint,
Loopback

72. Intermediate System - Intermediate System (IS-IS)
 Intermediate System - Intermediate System is a link state protocol similar to
OSPF and often used by Internet Service Providers.
 IS-IS utilizes a link state database and runs the SPF Dijkstra algorithm to
select shortest paths routes..
 IS-IS uses Dijkstra's algorithm for computing the best path through the network

73. Integrated IS-IS
 Integrated IS-IS is a version of the IS-IS
 Dual IS-IS
 Implementations send only one set of routing updates
 Supporting multiple network layer protocols in a router