Network Basics

Question 1

Name the 7 layers of the OSI model.

Answer 1

Application, presentation, session, transport, network, data, physical.

Question 2

Name the 4 layers of the TCP/IP model.

Answer 2

Application, transport, internet, network access/interface.

Question 3

What is DHCP?

Answer 3

Dynamic host configuration protocol

Discover, offer, request, acknowledgement.

Question 4

What are the five DHCP message types?

Answer 4

Discover-type1, offer-type 2, request-type 3, decline-type 4, and acknowledge-type 5.

Question 5

What is NAT? What are the types?

Answer 5

Network address translation. Used to translate private ip address to public ip address.
TYPES: 1 to 1, one to many, and many to many.

Question 6

What are the RFC 1918 private ip address ranges?

Answer 6

10.0.0.0/8
172.16.0.0/12
192.168.0.0/16

Question 7

What is the broadcast address of 172.16.50.10/22?
What is the host range?
What is the gateway address?

Answer 7

Broadcast - 172.16.51.255
Range - 172.16.48.1 - 172.16.51.254
Gateway- 172.16.48.1

Question 8

What is the block size of a /22?

Answer 8

4 hosts

Question 9

What is the block size /23?

Answer 9

2 hosts

Question 10

What is the block size of /24?

Answer 10

256 hosts

Question 11

What is the block size of /17?

Answer 11

128 hosts

Question 12

What is the block size of /18?

Answer 12

64 hosts

Question 13

What is the block size of /19?

Answer 13

32 hosts

Question 14

What is the block size of a /20?

Answer 14

16 hosts

Question 15

What is the block size of /21?

Answer 15

8 hosts

Question 16

How can you find the number of subnets with a specific subnet mask?

Answer 16

Convert the subnet bits to one’s, and count the number of ones bits.
Example: 255.255.192.0
2 to the power of 2 = 4
4 subnets are within a /18

Question 17

How do you find the number of usable hosts with a subnet?

Answer 17

Turn the host bits to one’s, and count the number of bits on.
Example: 255.255.192.0 = 14 host bits on.
2 to the power of 14 - 2 = 16,382

Question 18

What are the 5 well known TCP flags?

Answer 18

SYN
ACK
PUSH
FIN
RST

Question 19

What is ARP?

Answer 19

Address resolution protocol
Resolves IP to mac address

Question 20

What is RARP?

Answer 20

Reverse Address Resolution Protocol
Resolves mac address to IP.

Question 21

What is a TCP forced close flag called?

Answer 21

RST

Question 22

What is the TCP 4 way close?

Answer 22

FIN –>
ACK FIN
ACK

Question 23

What is the TCP flag that allows data to be sent?

Answer 23

PSH flag

Question 24

What is UDP?

Answer 24

User datagram protocol.
A connection-less protocol that is unreliable. Delivery of traffic is not guaranteed.

Question 25

What is an F5 self-ip?

Answer 25

An ip address assigned to an interface on the Big-IP.

Question 26

What is the command to look at networks learned by the Big-IP?

Answer 26

Tmsh net show route

Question 27

What is 802.1Q?

Answer 27

Protocol that carries vlan information in order to separate different networks. It is also known as vlan tagging.

Question 28

Do you need a vlan in order to configure a self-ip?

Answer 28

No, but the F5 will automatically assign a tag (vlan) if one isn’t specified.

Question 29

What is a non-floating self-ip?

Answer 29

The self-ip that is statically assigned to that Big-IP and does not move (float) in a HA configuration.

Question 30

What is a floating self-ip?

Answer 30

A self-ip shared between HA members, as it floats to the current primary member.

Question 31

What is a traffic group?

Answer 31

A collection of related configuration objects, such as floating ips, virtual ip addresses, and SNAT translation addresses. It’s purpose is to float to the current primary Big-IP to process application traffic.

Question 32

What are DHCP options?

Answer 32

They are client DHCP parameters, such as:
IP address
Subnet mask
Gateway
Lease time
DNS server address