OSI Layer 3 - Network Layer

Question 1

Layer 3 Overview

Answer 1

Responsible for routing packets to their destination & QoS

IP (Internet Protocol) is the best-known layer 3 protocol

Connectionless protocol with no acknowledgements at layer 3

Other Layer 3 Protocols: ICMP, IPsec

Question 2

IP Addressing

Answer 2

A logical addressing scheme implemented at layer 3

No logical separation between networks at layer 2, it’s done at layer 3

Question 3

Unicast/Broadcast/Multicast

Answer 3

Unicast - single destination host
Broadcast - all hosts on the subnet
Multicast - multiple interested hosts

Question 4

IPv4 Addresses

Answer 4

32 bits long

4 “octets” in dotted decimal format

192.168.10.15
Each octet - 8 bits long

Question 5

Subnet Mask

Answer 5

Defines the boundary between the network & host portion of an IP address

Question 6

Network Address

Answer 6

All 0’s in the host portion designates the network address

Not allowed to be allocated to a host

Question 7

Broadcast Address

Answer 7

Traffic sent to this address is sent to all hosts in the subnet
Final address in a subnet