Addressing on Networks

Question 1

Describe a MAC address in detail.

Answer 1

A MAC address operates at the Data Link layer and is embedded on every existing NIC. It is 48 bits long and written in hexadecimal notation separated by colons. The first 24 bits are the Organizationally Unique Identifier (OUI) and the last 24 bits make up the device ID which identifies the device itself.

Question 2

What is the difference between static IP addressing and Dynamic IP addressing?

Answer 2

A static IP address is assigned manually by the network administrator, while a dynamic IP address is automatically assigned (or leased) by a DHCP server

Question 3

What is a gateway?

Answer 3

A gateway is a device that nodes use to access another network. The default gateway is the device that nodes will turn to first.

Question 4

What is the subnet mask?

Answer 4

The subnet mask is a 32-bit number that is used to indicate what portion of an IP address is the network portion (network ID) and which is the host portion (host ID)

Question 5

What is Classful Addressing?

Answer 5

It is an older method of managing IP address ranges. The dividing line between the network and host portions is determined by the numerical range the IP address falls in.

Question 6

What are the private and public IP address ranges for Class A, B, and C?

Answer 6

Private:
Class A - 10.0.0.0 - 10.255.255.255
B - 172.16.0.0 - 172.31.255.255
C - 192.168.0.0 - 192.168.255.255

Public:
A - 1.x.x.x - 126.x.x.x
B - 128.0.x.x - 191.255.x.x
C - 192.0.0.x - 223.255.255.x

Question 7

What are some examples of reserved IP addresses?

Answer 7

0. 0.0.0 is an unassigned address.

169. 254.x.x is an APIPA address, which is assigned when DHCP fails to assign an IP address to a node.

Question 8

What are the benefits of Network Address Translation (NAT)?

Answer 8

NAT conserves the number of private IP addresses needed by a network by substituting the private IP addresses with a single public IP. This also improves security because the gateway can hide an entire network behind this single address.

Question 9

Port Address Translation (PAT)

Answer 9

Assigns a separate TCP port to each session between a local host and an Internet host.

Question 10

What are the 2 variations of NAT? How do they differ?

Answer 10

1. Static NAT (SNAT) - gateway assigns the same public IP to a host each time it makes a request to access the Internet.
2. Destination NAT (DNAT) - hosts outside the network will address a node inside the network by a predefined public IP address.

Question 11

Why were IPv6 standards originally developed?

Answer 11

Improve routing capabilities and speed of communication over IPv4 standards, and to allow more public IP addresses on the Internet.

Question 12

What are some characteristics of IPv6 addressing?

Answer 12

• 128 bits written as 8 blocks in hexadecimal form.
• Each block is 16 bits. If a block contains all 0s, they can be eliminated and replaced with a double colon (this can only be done once).
• The last 64 bits (4 blocks) of the address identify the interface, and is called the Interface ID.

Question 13

What does it mean when a network is dual stacked?

Answer 13

It means that the network is configured to use both IPv4 and IPv6 protocols.

Question 14

What are the 2 types of unicast addresses used by IPv6?

Answer 14

1. Global address - can be routed on the internet, similar to public IPv4 addressing. Generally begins with 2000::/3
2. Link Local Address - Can be used for communicating with nodes in the same link (LAN), similar to APIPA. Generally begins with FE80::/10

Question 15

multicast address

Answer 15

Delivers packets to all nodes in the targeted multicast group.

Question 16

anycast address

Answer 16

Identifies multiple destinations, with packets being delivered to the closest destination

Question 17

List the 3 steps for IPv6 Autoconfiguration.

Answer 17

1. Computer creates its IPv6 address. The first 64 bits are either randomly generated or generated from the network adapter’s MAC address.
2. Computer checks to make sure its IP address is unique on the network.
3. The computer then asks if a router on the network can provide configuration info.

Question 18

What is a socket?

Answer 18

A socket consists

of both a host’s IP address and the TCP/UDP port of a process, separated by a colon.

Question 19

Ports are divided into what 3 types? What are their port number ranges?

Answer 19

1. Well-known ports range from 0 to 1023, widely used by well-known applications.
2. Registered ports range from 1024 to 49151
3. Dynamic + private ports range from 49152 to 65535. Open for use without restriction

Question 20

Name Resolution

Answer 20

The process of discovering the IP address of a host whose Fully Qualified Domain Name (FQDN) is known.

Question 21

Why does DNS follow a distributed database model rather than a centralized model?

Answer 21

If a handful of servers experience errors, DNS will not fail catastrophically since data is being distributed over thousands of servers.

Question 22

Primary DNS Server

Answer 22

The authoritative name server for an organization, which holds the authoritative DNS database for the organization’s zones.

Question 23

Secondary DNS Server

Answer 23

A backup authoritative name server for the organization. Receives updates from the primary DNS server, called a zone transfer.

Question 24

Caching DNS Server

Answer 24

A server that accesses public DNS data and caches the DNS information it collects. They do not store zone files, therefore they do not participate in zone transfers.

Question 25

Forwarding DNS server

Answer 25

An optional server that receives queries from local clients but doesn’t work to resolve those queries.

Question 26

What port number, OSI model layer, and protocol do DNS messages use

Answer 26

Application layer, port 53, uses UDP.

Question 27

What is the difference between a recursive query and an iterative query?

Answer 27

A recursive query demands a resolution or the answer “it cannot be found.” An iterative query does not demand resolution; servers will only provide information if they have it.

Question 28

A (Address) Record and AAAA record

Answer 28

Both store the name-to-address mapping for a host. A is for IPv4 addresses and AAAA is for IPv6 addresses.

Question 29

CNAME Record

Answer 29

Canonical Name record. Holds alternative names for a host.

Question 30

PTR record

Answer 30

Pointer record, used for reverse lookups (provide address information if you know the IP address). Generally stored in a reverse zone by an ISP.

Question 31

NS record

Answer 31

Name server record, indicates the authoritative name server for a domain.

Question 32

MX record

Answer 32

Mail exchanger record, identifies an email server, used for email traffic.

Question 33

SRV record

Answer 33

Service record, identifies the hostname and port of a computer that hosts a specific network service besides email.

Question 34

TXT record

Answer 34

Text record, holds any type of free-form text. Most often used by Sender Policy Framework (SPF) or Domainkeys Identified Mail (DKIM)

Question 35

Demilitarized Zone (DMZ)

Answer 35

The area between 2 firewalls, unprotected. External DNS server is often located here.

Question 36

PING (Packet Internet Groper)

Answer 36

A command that is used to verify that TCP/IP is installed, bound to the NIC, configured correctly, and communicating with the network. Sends out a signal called an echo request to another computer, which is basically a request for response. uses ICMP (Internet Control Message Protocol)

Question 37

ipconfig and ifconfig

Answer 37

Shows current TCP/IP addressing and domain name information on a system. ipconfig is for Windows systems, ifconfig is for Linux systems. and only shows TCP/IP settings.

Question 38

nslookup (name space lookup)

Answer 38

A utility that allows you to query the DNS database from any computer on the network and find the host name of a device by specifying its IP address or vice-versa.

Question 39

dig (domain information groper)

Answer 39

A utility for Linux and MacOS systems. Similar to nslookup but provides more detailed information.

Question 40

What is an exhausted DHCP scope?

Answer 40

When a DHCP scope is exhausted, it means that all available addresses are used up which prevents new clients from connecting to the network. This can be caused by leases being too long.