topic 6B : ipv4 addressing (II)

Question 1

network address

Answer 1

• first address of a network/subnet
• convert all the host bits to 0
• identity address for the subnet
• cannot be assigned to network interfaces (cannot be used as an IP address for a device in the network)

Question 2

broadcast address

Answer 2

• convert all the host bits to 1
• used to send data to all hosts
• cannot be assigned to network interfaces (cannot be used as an IP address for a device in the network)

Question 3

first and last host address

Answer 3

• usable range which can be assigned to network interfaces
• network address + 1 = first host address
• broadcast address - 1 = last host address

Question 4

formula for number of hosts/size of the subnet

Answer 4

number of usable hosts = 2^h - 2
where h = number of host bits

Question 5

unicast transmission

Answer 5

the process of sending a packet from one host to an individual host

Question 6

broadcast transmission

Answer 6

the process of sending a packet from one host to all hosts in the network
! : routers do not forward a limited broadcast

Question 7

multicast transmission

Answer 7

the process of sending a packet from one host to a group of hosts in the network which subscribes to a special range of addresses (known as multicast addresses)

Question 8

private ipv4 ranges

Answer 8

hosts that do not require direct access to the internet can use private addresses
- 10.0.0.0 to 10.255.255.255 (10.0.0.0/8)
- 172.16.0.0 to 172.31.255.255 (172.16.0.0/12)
- 192.168.0.0 to 192.168.255.255 (192.168.0.0/16)

Question 9

public address blocks

Answer 9

most other addresses (outside of the private address ranges) are publicly accessible from the internet

Question 10

special ipv4 addresses (1)

Answer 10

1) network and broadcast addresses : within each network the first and last addresses cannot be assigned to hosts

2) loopback addresses : 127.0.0.1 is a special address that hosts use to direct traffic to themselves
(127.0.0.0 to 127.255.255.255 are reserved)

3) link-local address : 169.254.0.0 to 169.254.255.255 (169.254.0.0/16) addresses can be automatically assigned to the local host

Question 11

special ipv4 addresses (2)

Answer 11

4) TEST-NET addresses : 192.0.2.0 to 192.0.2.255 (192.0.2.0/24) set aside for teaching and learning purposes

5) experimental addresses : 240.0.0.0 to 255.255.255.254 are listed as reserved

Question 12

Class A addresses

Answer 12

• uses a fixed /8 prefix : 8-bit network and 24 bits for hosts
• only 128 possible class A networks = 0.0.0.0 /8 to 127.0.0.0 /8

Question 13

class B addresses

Answer 13

• uses a fixed /16 prefix : 16-bit network and 16 bits for hosts
• address block for class B = 128.0.0.0/16 to 191.255.0.0 /16

Question 14

class C addresses

Answer 14

• uses a /24 prefix : 24-bit network and 8 bits for hosts
• address block for class C = 192.0.0.0 /24 to 223.255.255.0 /24

Question 15

problems of legacy classful addressing

Answer 15

• insufficient for modern world
• a company that needs 260 addresses will be assigned a class B block which leads to wastage of many addresses

Question 16

classless addressing

Answer 16

• formal name is CIDR (classless inter-domain routing)
• created a new set of standards that allow service providers to allocate ipv4 addresses on any address bit boundary (prefix length)

Question 17

classless ipv4 addressing

Answer 17

• newer technology
• subnet mask determines the network portion and the host portion
• value of first octet does not matter
• currently used within the internet and in the most internal networks