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NETWORKING
FUNDAMENTALS

K.GAYATHRI

IPv4 Addressing
The IPv4 addresses are unique and universal.

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An IPv4 address is 32 bits long.

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The address space of IPv4 is 232 (4,294,967,296)

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2 Types of IPv4 Notations.
Binary notation

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Dotted-decimal notation

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SUBNETTING AND VLSM
Subnetting
Divide a large address block into smaller subgroups.
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Use of flexible net mask.

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VLSM-Variable Length Subnet Mask
Technique that allows network administrators to
divide an IP address space into subnets of different
sizes, unlike simple same-size Subnetting.
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Subnetting a subnet.

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ROUTING PROTOCOLS
Routing Protocol

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Protocols used by routers to make path determination choices
and to share those choices with other routers
Autonomous system (AS)

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Uses Interior Gateway Protocols as routing protocols
A group of routers under the control of a single administration
Interior Gateway Protocols (IGPs)

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Routing protocols used within an AS
Exterior Gateway Protocols (EGPs)

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Routing protocols used to route information between multiple
autonomous systems

ROUTING PROTOCOLS(continued)
Examples of IGPs
Routing Information Protocol (RIP)

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Enhanced Interior Gateway Routing Protocol
(EIGRP)
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Open Shortest Path First (OSPF)

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Example of EGP
Border Gateway Protocol (BGP)

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ROUTING INFORMATION PROTOCOL(RIP)
Routing Information Protocol (RIP)

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The easiest Interior Gateway Protocol to configure is RIPv1

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A distance-vector routing protocol that broadcasts entire routing
tables to neighbors every 30 seconds
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RIP has a maximum hop count of 15

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As a result, RIP does not work in large internetworks

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Enabling RIP Routing, the following commands are used,

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Router(config)#router rip
Router(config-router)#network 192.168.1.0
To troubleshoot RIP Routing,

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Router#show ip rip

ENHANCED INTERIOR GATEWAY PROTOCOL(EIGRP)
EIGRP is a Cisco-proprietary Hybrid routing protocol, incorporating
features of both Distance-Vector and Link-State routing protocols.
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It sends routing updates only when network topology changes instead
of its entire routing table at regular intervals.
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Its convergence is very fast

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It supports classless inter-domain routing (CIDR) and variable-length
subnet masks
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(VLSM)
EIGRP Major Drawback

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It is Cisco proprietary - it does not inter-operate with other vendors'
devices. This, of course, is the big one. If you are working in a mixed
environment, EIGRP doesn't make as much sense

EIGRP(Continued)
EIGRP uses Diffusing Update Algorithm (DUAL)to determine
the best path among all “feasible” paths. DUAL also helps ensure
a loop-free routing environment.
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EIGRP will form neighbor relationships with adjacent routers in
the same Autonomous System (AS)
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EIGRP traffic is either sent as unicasts, or as multicasts on
address 224.0.0.10, depending on the EIGRP packet type.
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Reliable Transport Protocol (RTP) is used to ensure delivery of
most EIGRP packets.
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EIGRP packets are Hello,Update,Query,Reply and Ack

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EIGRP(Continued)
EIGRP, much like OSPF, builds three separate tables,
Neighbor table– list of all neighboring routers. neighbors must belong
to the same Autonomous System
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Topology table– list of all routes in the Autonomous System

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Routing table– contains the best route for each known network

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Enabling EIGRP Routing, the following commands are used,

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Router(config)#router eigrp 100
Router(config-router)#network 10.10.1.0
To troubleshoot EIGRP Routing,following commands are used,

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Router#show ip route eigrp
Router#show ip eigrp neighbor
Router#show ip eigrp traffic

OPEN SHORTEST PATH FIRST(OSPF) PROTOCOL
OSPF is a standardized Link-State routing protocol,designed to
scale efficiently to support larger networks
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Special routers (autonomous system boundary routers) or
backbone routers responsible to dissipate information about other
AS into the current system.
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It minimizes routing table entries by dividing AS into areas

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Fast convergence Protocol

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Low bandwidth requirements

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Supports different types of areas

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Route summarization and authentication

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Cisco's implementation is fully compliant with the specification
OSPF v2.
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OSPF(Continued)
OSPF Packet Types,
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Hello packets

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Database Description (DBD)

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Link-State Request (LSR)

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Link-State Update (LSU)

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Link-State Acknowledgement (LSA)

Different Types of LSAs,
Router LSA

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Network LSA

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Network Summary LSA

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ASBR Summary LSA

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AS-External LSA

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OSPF(Continued)
Enabling OSPF Routing, the following commands are used,

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Router(config)#router ospf 1(process id)
Router(config-router)#network 192.168.1.1 0.255.255.255 area 1
To troubleshoot OSPF Routing,following commands are used,

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Router# show ip route
Router# show ip ospf
Router# show ip ospf interface
Router# show ip ospf neighbor
Router# show ip ospf database

BORDERED GATEWAY PROTOCOL(BGP)
Routing Protocol used to exchange routing information between
Autonomous System
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Exterior gateway protocol and path vector protocol

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A Path vector protocol defines a route as a pairing between a
destination and the attributes of the path to that destination
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Types of BGP Messages are Open,update, Keep-alive and
Notification
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Two types of BGP
External BGP Peering (eBGP)
Internal BGP Peering (iBGP)

BGP(Continued)
Internal BGP (iBGP)
BGP peer within the same AS

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Not required to be directly connected

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iBGP speakers need to be fully meshed

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They originate connected networks

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They do not pass on prefixes learned from other iBGP
speaker
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External BGP Peering (eBGP)
Between BGP speakers in different AS

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Should be directly connected

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Do not run an IGP between eBGP peers

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SWITCHING IN VLAN'S
Switches also have enabled the creation of Virtual LANs (VLANs).

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VLANs provide greater opportunities to manage the flow of traffic on the
LAN and reduce broadcast traffic between segments.
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VLANs are groups of computers in an intelligent switched network.

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Allow us to split switches into separate (virtual) switches

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Only members of a VLAN can see that VLAN’s traffic

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VLAN'S Types,
Port-based VLANs

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MAC address based

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Protocol based VLANs

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Application based VLANs

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VIRTUAL TRUNKING PROTOCOL(VTP)
VTP reduces the complexity of managing and monitoring VLAN networks

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VTP maintains VLAN configuration consistency across a common network
administration domain
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VTP allows VLANs to be trunked over mixed media

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VTP provides for accurate tracking and monitoring of VLANs

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VTP provides “Plug-and-Play” configuration when adding new VLANs

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VTP switches operate in one of three modes:
Server – default mode. Sends VLAN information to other switches.

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Client – receives VLAN information and forwards it to other switches.

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Transparent – forward VTP traffic but do not originate or use it. They can have their
own VLANs, not shared with other switches.
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VTP(Continued)
Command to set the VTP mode:
Switch(vlan)#vtp {client | server | transparent}
VTP Pruning-VTP pruning increases network available
bandwidth by restricting flooded traffic to those trunk
links that the traffic must use to reach the destination
devices
VLAN3
VLAN1

VLAN4
VLAN2

SPANNING TREE PROTOCOL(STP)
STP is a link management protocol that provides path
redundancy while preventing undesirable loops in the
network
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Spanning Tree Algorithm
The switches use this algorithm to decide which ports
should be shut down.
Choose one switch to be “root bridge”

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Choose a “root port” on each other switch

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Choose a “designated port” on each segment.

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Close down all other ports.

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STP TYPES
1.CSTP-Comman STP
2.RSTP(Rapid STP)-RSTP(Rapid Spanning Tree Protocol-802.1w
Standard): it is the enhanced protocol of STP,the main caracteristic
of this one is Faster than STP (it converge in less than 6 seconds).
3.MST(Multiple STP)-allows multiple spanning tree domains to be
configured in a network and on a switch.It is based on RSTP, and is
backwards-compatible with RSTP and STP.
4.PVST(Per VLAN STP)- Maintains a spanning-tree instance for
each VLAN configured in the network.
5.PVST+ -Per-VLAN Spanning Tree Plus is a Cisco
proprietary spanning tree protocol based on STP.

VIRTUAL PRIVATE NETWORK(VPN)
Creates a secure tunnel over a public network

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Uses the Internet as the public backbone to access a

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secure private network
Remote employees can access their office network

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VPN Protocols
PPTP (Point-to-Point tunneling Protocol)

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L2F (Layer 2 Forwarding Protocol)

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L2TP (Layer 2 Tunneling Protocol)

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IPSec (Internet Protocol Security)

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IPsec(IP security)
Provides Layer 3 security (RFC 2401)

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Transparent to applications (no need for integrated IPSec
support)
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A set of protocols and algorithms used to secure IP data at the
network layer
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Combines different components:
Security associations (SA)

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Authentication headers (AH)

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Encapsulating security payload (ESP)

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Internet Key Exchange (IKE)

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Ipsec Modes
Tunnel Mode
Entire IP packet is encrypted and becomes the data component
of a new (and larger) IP packet.
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Frequently used in an IPsec site-to-site VPN

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Transport Mode
Ipsec header is inserted into the IP packet

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No new packet is created

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Works well in networks where increasing a packet’s size could
cause an issue
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Frequently used for remote-access VPNs

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Networking Fundamentals

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