routing fundamentals and subnets introduction to it and communications technology ce00378-1
TRANSCRIPT
Routing Fundamentals and Subnets
Introduction to IT and Communications Technology
CE00378-1
Content Describe routed protocols List the steps of data encapsulation in an internetwork as
data is routed to Layer 3 devices Describe connectionless and connection-oriented
delivery Name the IP packet fields Describe how data is routed Compare and contrast different types of routing protocols List and describe several metrics used by routing
protocols List several uses for subnetting Determine the subnet mask for a given situation Use a subnet mask to determine the subnet ID
IP Address A packet of data can be sent to a particular
network by ANDing it with the network MaskFor a Class C Address this would be
255.255.255.0All of the bits which represent the network ID are
set to 1 the rest are set to 0When the IP address converted to binary is AND’d
with the network mask only the Network ID is displayed
This network address can then be used for routing the packet to the correct interface
IP Address Example
IP address grouping
•All of these addresses can be represented in a routing table by the network address•192.168.10.0
•Rather than the full 254 addresses which could be added
Routed protocol A routed protocol
Is one where it is used carry out addressing across the network
The most common example would be IP
Network layer devices in data flowE
ncap
sula
te Decapsulate
A IP Packet being transferred across a network with three routers
Router protocol stripping As a packet of information is transported
between two pointsThe level 1 and 2 frame information will be
stripped and replacedThis can be done due to a different technology
being connected on the next segment of the journey
It may be changing the header with the address of the next point on the route
The IP and above layers (3 to 7) will remain the same throughout the transport of the packet
Router protocol stripping Example
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Connectionless network services•In connectionless services the packets are just transferred between devices
•No communications are agreed before sending data, all of the packets may take different routes to the same destination based on local conditions•Commonly referred to as Packet switched communications
Connection orientated services•In connection orientated services, the route is worked out before communications start
•A telephone network is an example of this•Commonly referred to as Circuit Switched networks
Network layer fields
All of the field lengths are fixed except for IP Options and Padding fields
•The most common Network layer (Routed) protocol is IPv4 at the moment•Below is the layout of the protocol with the additional information which needs to be transferred with the data element
Routing metrics•The routing metrics are the values which are used to work out the best route between two points when offered more than one route
•Metrics can be•Delay•Hop Count•Bandwidth•Load•Cost•Reliability
Data encapsulation Encapsulation
Is the adding of information to the packet Decapsulation
Is the removal of this information
En
cap
sulation
Dec
apsu
latio
n
The network layer routing•The switch will allow routing in the local LAN
•A packet of information will be forwarded out of a particular interface based on the MAC address of the device attached to it
•Routers forward based on the IP address (Network layer) information
Layer 2 switching & layer 3 routing
ARP tables & routing tables
Router and switch feature comparison
Routed protocol
Routing protocol•A routing protocol is used to work out the best route based on metrics between multiple points
Routing process
Routing tables
Routing algorithms and metrics
Interior & exterior gateway protocols
Link-state & distance-vector
Distance Vector protocols Use the distance, direction and vector to any point in the network
RIP Distance Vector
IGRP Distance Vector
EIGRP Distance Vector
Link State protocols Send periodic updates to the network regarding the knowledge they
have OSPF
Link State
IP address bit patternsIP Protocols are made up two parts
NETWORK ID and Host IDDepending on the class is how many bits are represented by each part
IP Subnets IP Addresses are made up of
Network ID Host ID Depending on the class this dictates the size of each
element. The host ID part though can be split again to extend
the length of the Network ID Example would be a Class C address by default
Network ID is 24 bits and Host ID is 8 bits By borrowing bits from the host id the network ID is expanded
The disadvantage is that the number of possible hosts are reduced hosts
Subdividing the host octets of a class C address
Subdividing the host octets of a class B address
Subdividing the host octets of a class A address
Subnetting chart (bit position and value)
Subnetting chart for a class C address (subnet mask identifier)
Subnetting
Subnetting chart
Subnet scheme
Borrowing 3 bits – therefore subnetwork addresses go up in multiples of 32
Subnetting chart
•The logical ANDing process•This process is used to work out the network part of the IP address for routing purposes
Calculating the subnet ID
Summary of lecture
IP AddressingRouting of these protocols Subnets Class C
Routing Protocols Serial Interfaces for WAN’s