Introducing the TCP/IP Internet Layer, IPv4 Addressing, and Subnets

Question 1

What is the range of Class A addresses?

Answer 1

First Octet of 1 - 126
/8

Question 2

What is the range of Class B addresses?

Answer 2

First Octet of 128 - 191
/16

Question 3

What is the range of Class C addresses?

Answer 3

First Octet of 192 - 223
/24

Question 4

What is the range of Class D addresses and what are they reserved for?

Answer 4

First Octet of 224 - 239

Multicast

Question 5

What is the range of Class E addresses and what are they reserved for?

Answer 5

First Octet of 224 - 255

Experimental

Question 6

What addresses are reserved and allocated of private use? What RFC did this?

Answer 6

RFC 1918 - “Address Allocation for Private Internets”

A - 10.0.0.0 /8

B - 172.16.0.0 /12

C - 192.168.0.0 /16

Question 7

What address range do Microsoft and Apple operating systems default to if they fail to get a DHCP address, what RFC defined this? What is the feature called?

Answer 7

RFC 3927 - 169.254.0.0 /16

Automatic Private IP Addressing (APIPA)

Question 8

What is the local loopback address range?

Answer 8

127.0.0.0 /8

Typically used as 127.0.0.1

Question 9

What two address ranges are assigned for use in documentation and example code, what RFC defined this?

Answer 9

RFC 5737

198. 51.100.0/24
199. 0.113.0 /24

Theses ranges do not appear on the public internet.

Question 10

What is the address 0.0.0.0 used for and what RFC defined this?

Answer 10

RFC 5735

0.0.0.0 indicates the host in “this” network and only used as a source address.

A common use is during the DHCP assignment process before the host has a valid IPv4 address.

Question 11

What is a directed broadcast? What kind of attack did this lead to in the 1990s? What command did Cisco implement by default to help prevent this?

Answer 11

A directed broadcast is the last address in a network. It could be used by an device outside of it’s own network to force traffic to all devices within it’s network.

This was a way users created denial of service (DoS) attacks referred to as Smurf.

Cisco implemented the command: no ip directed-broadcast by default starting with Cisco IOS Release 12.0

Question 12

What is the local broadcast address and what does it do?

Answer 12

255.255.255.255

It allows devices to send traffic to this address which will then go out to all other devices within it’s own network or subnet.

Question 13

How do you verify the IPv4 address of a host on Apple Mac?

Answer 13

System Preferences > Network > (click on a connection) > Advanced > TCP/IP tab

or

Go > Utilities > Terminal > ifconfig {interface name}

Question 14

How do you verify the IPv4 address of a host in Linux?

Answer 14

Go to the command line / terminal > ifconfig

Also, to view info on most commands you type in “man” in front. Such as - man ifconfig

Question 15

What are the benefits of VLSM?

Answer 15

Efficiently using IP addresses

Support for route summarization (aka route aggregation), meaning smaller routing tables and quicker route calculations.