2. Network +
Introduction to Networking
What is a network :
The word “ network “ means, “ two computers are connected using a
transmission media and are able to share their resources, transfer data.
The transmission media for the term network is either cable media or
wireless media.
Advantage of Networking :
1. Resource sharing : buy devices for all computers in same network, not
one device for one computer.
2. High reliability : all files can be copied to two or more machines, if one
goes down, we can use other.
3. Communication media : using the media. Two or more devices can be
interconnected to share resources & exchange information.
4. High speed : information can be synchronized when one user makes
changes to on line document, the other can see the change immediately.

3. Layer 3 Device. Works at the Network Layer
Forwards Data packets based on IP Address
This allows Routers to choose the best path thru the Network
Important Traffic regulating device on large Networks
Can have inbuilt security features-Firewall,Authentication.

4. 1. A router is a device which is used in our network to
connect two different networks.
2. Routers, by default, will not forward any broadcasts.
3. Routers use the logical address in a network layer to
determine the next hop router or a host which is
located on a remote place.
4. Routers can use access lists, created by an
administrator, to control security on the types of
packets that are not allowed to enter or exit an
interface.

5.  The algorithm used for the routing protocols
defines the following processes:
 Mechanism for sending and receiving routing
information.
 Mechanism for calculating the best paths and installing
routes in the routing table.
 Mechanism for detecting and reacting to topology
changes.

7.  Classless (Use of VLSM) or Classful - Classless routing
protocols include the subnet mask in the updates.
 This feature supports the use of Variable Length Subnet Masking
(VLSM) and better route summarization.
 Classful routing protocols do not include the subnet mask and
cannot support VLSM.
 Time to Convergence - Time to convergence defines how
quickly the routers in the network topology share
routing information and reach a state of consistent
knowledge.
 The faster the convergence, the more preferable the protocol.
 Scalability - Scalability defines how large a network can
become based on the routing protocol that is deployed.
 The larger the network is, the more scalable the routing protocol
needs to be

8.  Resource Usage - Resource usage includes the
requirements of a routing protocol such as memory
space, CPU utilization, and link bandwidth
utilization
 Higher resource requirements necessitate more powerful
hardware to support the routing protocol operation in
addition to the packet forwarding processes.
 Implementation and Maintenance - Implementation
and maintenance describes the level of knowledge
that is required for a network administrator to
implement and maintain the network based on the
routing protocol deployed.

10. Static Routing
The command syntax
Ip route [ destination_network] [ Destination subnet mask ] [
<next hop ip address >or <exit interface type><No.> ]
This list describes each command in the string
ip route : the command used to create the static routing.
destination_network : the network you are placing in the
routing table.
mask : the subnet mask being used on the network.
next hop address : the address of the next hop router that will
receive the packet and forward it on the remote network.

13.  A router using a distance vector routing
protocol does not have the knowledge of the
entire path to a destination network.
 The router only knows
 The direction or interface in which packets should be
forwarded and
 The distance or how far it is to the destination
network

14.  Some distance vector routing protocols call for
the router to periodically broadcast the entire
routing table to each of its neighbors.
 This method is inefficient because the updates
not only consume bandwidth but also consume
router CPU resources to process the updates.

15. Distance Vector Routing Protocols

16. 16
1. Each router establishes a relationship (“adjacency”)
with its neighbors
2.Each router generates link state advertisements (LSAs)
which are distributed to all routers
LSA = (link id, state of the link, cost, neighbors of the link)
3. Each router maintains a database of all received
LSAs (topological database or link state database), which
describes the network has a graph with weighted
edges
4. Each router uses its link state database to run a
shortest path algorithm (Dijikstra’s algorithm) to
produce the shortest path to each network

17. 17
 With distance vector routing, each node has
information only about the next hop:
 Node A: to reach F go to B
 Node B: to reach F go to D
 Node D: to reach F go to E
 Node E: go directly to F
 Distance vector routing makes
poor routing decisions if
directions are not completely
correct
(e.g., because a node is down).
 If parts of the directions incorrect, the routing may be incorrect until the
routing algorithms has re-converged.
A B C
D E F

18. 18
 In link state routing, each node has a complete map
of the topology
 If a node fails, each
node can calculate
the new route
 Difficulty: All nodes need to
have a consistent view of the
network
A B C
D E F
A B C
D E F
A B C
D E F
A B C
D E F
A B C
D E F
A B C
D E F
A B C
D E F

24. Enhanced IGRP is a distance vector routing protocol. Why it is called enhanced IGRP.
Because like IGRP, EIGRP uses the concept of an autonomous system to describe the
set of contiguous routers that run the same routing protocol and share routing
information. But unlike IGRP, EIGRP includes the subnet mask in its route updates.
EIGRP is some times referred to as a Hybrid routing protocol. EIGRP has a maximum
hop count of 255.
There are no. of powerful features for EIGRP, the main ones are listed here :
It uses max hop count of 255
It is a classless routing protocol
It is sometimes referred to as a hybrid routing protocol
Like IGRP, EIGRP uses AS ( autonomous system number ) to share it’s routing table.
EIGRP uses RTP ( Reliable Transport Protocol ) for communication
It uses Dual ( Diffusing update algorithm ) for the selection of best path
Supports all layer 3 protocols(IPv4,IPX and IPv6)
Supports VLSM/CIDR

27. Configuring OSPF :
These two elements are the basic elements of OSPF configuration :
Enabling OSPF
Configuring OSPF areas
Enabling OSPF
Router( config )# router ospf ?
<1-65535>
A value in the range 1-65535 identifies the ospf process ID. It’s a unique no.
on this router that groups a series of ospf configuration commands under a
specific process. Different ospf routers don’t have to use the same process ID
in order to communicate.
Configuring OSPF areas
Router# config t
Router( config t )# router ospf 1
Router( config – router )# network 10.0.0.0 0.255.255.255 area 0