IP Addresses
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What is an IP address
A 32 bit long binary number globally unique to each device
How was an IP address made to be user friendly
It was split into 4 8 bit chunks with each octet being converted into denary The 4 values are then written with a dot between them; referred to as dotted decimal notation
What are the initial bits of the IP address referred to as
The network id The initial bits are the same for all devices (hosts) on a particular network.
What are the remaining bits in the IP address referred to as
The host id Used to identify a particular host in that network
What does a router do when it sees an IP packet
Examines the network part of address to identify best path forward for the packet
What happens to an IP packet when it arrived at its destination network
Host bits are examined to ensure its sent to correct device on the network
What must be true on any network or subnet
Network id must be identical for all hosts Host id must be different Number of bits allocated to network id is specified by subnet mask
How is a subnet mask written
Contains 1s in the position of network id and 0s in position of host id
Examples of how subnet masks are written
11111111 11111111 00000000 00000000 OR 255.255.0.0 This means the first 16 bits are the network id 255.192.0.0 means the first 10 bits are network id
What is a newer notation of writing a subnet mask
Used a slash and number of bits appended to actual address E.g. 172.16.200.12/12 means the first 12 bits are the network id
What addresses are reserved on any given network
An address with host bits of all 0’s and of all 1’s
What does it mean if the host bits are set to all 0s
The address refers to the network itself Routers use network address to direct packets to a given network
What does it mean for the host bits are all 1s
Means its the broadcast address Needed to send messages to all the devices in a given network
How can you calculate the maximum number of hosts on any network
2^n - 2 where n is the number of host bits
Relationship between length of network id and length of host id
The greater the length of the network id, the shorter the length of the host id, so a lower number of max hosts can be on a network E.g. network id = 24 bits host id = 8 bits 2^8 - 2 = 254 Network id = 12 bits host id = 20 bits 2^20 - 2 = 1,048,574
What is IPv4
The IP version which uses 32-bit address structure and has been used for over 4 decades
What is IPv6
A newer IP version that allows for a greater amount of addresses There are 3.4x10^38 possible addresses compared to 4.3x10^9 possible addresses with IPv4
Why was IPv6 developed
We were running out of unique addresses so more needed to be made
How are IPv6 addresses written
Written as 32 hex digits in blocks of 4 E.g. 2001:0db8:0000:0042:0000:8a2e:0370:7334
Structure of IPv6
Similar to IPv4, initial bits specify network and following specify the host
What do IPv6 and IPv4 offer together
As both systems can be ran parallel, offers a number of improvements with security
What needs to happen for networks to operate efficiently
Devices need to be able to determine quickly whether data is to be transmitted to another device on same network or device on a different network
What is a subnet mask used for
‘Masks out’ host bits of IP address and reveals network to which the device belongs
How is ‘ masking out’ performed
Carried out by AND operation on IP address and subnet mask