Network Layer Flashcards
What is the function of the internet layer
Handles routing, addressing, and encapsulation of packets.
What are the key tasks of the internet layer
- Encapsulation – Adds IP headers to data.
- Addressing – Assigns unique IP addresses.
- Routing – Directs packets across networks.
- Decapsulation – Removes IP headers at the destination.
What is an IPv4 address
A 32-bit address that uniquely identifies a device on a network.
How are IPv4 address structured
Four octets (8-bit each) separated by dots (e.g., 192.168.1.1).
Range: 0.0.0.0 to 255.255.255.255.
How is an IPv4 address structured
- Network portion (Identifies the network).
- Host portion (Identifies individual devices).
- Defined by Subnet Mask (e.g., /24 means first 24 bits are network).
What is an example of a subnet division
Network Address: 192.168.1.0
Broadcast Address: 192.168.1.255
Host Range: 192.168.1.1 - 192.168.1.254
What range can host devices be in for the final number
1-254
What is the broadcast and network address numbers
for network it is when the last number is 0 (all bits 0)
for broadcast its when all bits are 1 (all bits 1)
What are the key fields in an IPv4 header
IP Version (4).
Packet Length (Header + Data).
Source & Destination IPs.
TTL (Time-to-Live) – Limits packet lifespan.
Protocol Type (TCP=6, UDP=17, ICMP=1).
What is subnetting
Dividing a network into smaller logical networks.
How is the number of subnets calculated
2^borrowed bits (bits taken from host portion).
How does subnetting affect hosts per subnet
/24 → 254 hosts.
/26 → 62 hosts.
/28 → 14 hosts.
What is the difference between public and private IPs
Public IPs are internet routable while private IPs are only for local networks
What is the function of a subnet mask
Defines which part of an IP address is the network and which is the host.
What is the purpose of CIDR
Allows flexible subnetting and efficient IP allocation.
Why is flow control used for TCP data transfer?
a) to synchronize equipment speed for sent data
b) to synchronize and order sequence numbers so data is sent in complete numerical order
c) to prevent the receiver from being overwhelmed by incoming data
d) to synchronize window size on the server
e) to simplify data transfer to multiple hosts
C
to prevent the receiver from being overwhelmed by incoming data
Host1 is in the process of setting up a TCP session with Host2. Host1 has sent a SYN message to begin session establishment?
a) Host1 sends a segment with the ACK flag = 0, SYN flag = 0 to Host2.
b) Host1 sends a segment with the ACK flag = 1, SYN flag = 0 to Host2.
c) Host1 sends a segment with the ACK flag = 1, SYN flag = 1 to Host2.
d) Host2 sends a segment with the ACK flag = 0, SYN flag = 1 to Host1.
e) Host2 sends a segment with the ACK flag = 1, SYN flag = 0 to Host1.
f) Host2 sends a segment with the ACK flag = 1, SYN flag = 1 to Host1.
f
Host2 sends a segment with the ACK flag = 1, SYN flag = 1 to Host1.
What is a process
a running application
What is the difference between the transport layer and network layer
- Transport layer is used by devices to connect processes
- While the network layer enables devices to reach each other
What is the key function of routing
how to determining the best path
Assume a host with IP address 10.1.1.10 wants to request web services from a server at 10.1.1.254. Which of the following would display the correct socket pair?
a) 1099:10.1.1.10, 80:10.1.1.254
b) 10.1.1.10:80, 10.1.1.254:1099
c) 10.1.1.10:1099, 10.1.1.254:80
d) 80:10.1.1.10, 1099:10.1.1.254
c) 10.1.1.10:1099, 10.1.1.254:80
Client_IP:Client_Port → Server_IP:Server_Port
What is an IPv4 address
32-bit - uniquely identifies a device on an IP network
Which two of the following are invalid IPv4 addresses? a) 10.0.0.1
b) 200.255.255.111
c) 234.0.367.1
d) 172.16.254.1
e) 192.168.30.12.1
c, e
What us the prefix length
its the number of bits representing the network portion
Ex:192.168.1.1/24
ie the 24 is split by 3 8 bits(network portion), leaving 1 8 bit for host(portion)
What is the subnet mask
1s represent the network portion and 0s for host portion:
Ex:11111111.11111111.11111111.00000000
255 . 255 . 255 . 0
What is the network address
all host portion bits are zero
What is the broadcast address
all host portion bits are ones
What is the host address
between network and broadcast
Given 200.100.50.31/24, find out:
1. The network address
……………………………………………………….
2. The broadcast address
……………………………………………………….
3. The range of valid host addresses
……………………………………………………….
- 200.100.59.0
- 200.100.59.255
- 200.100.59.1-254
What is subnetting
Dividing a single address block into multiple logical networks
What is the formula for number of subnets
2^b , b being the number of bits borrowed
What is the formula for the number of hosts
2^hosts bits - 2
Example of borrowing 3 bits
Quick Method
Network
N (24) H (8) 192.168.1.0 /24
* Number of Subnets [2b] - borrowing 3 bits => 23 = 8 Subnets
* Host portion bits (h): (32-27) = 5
* Add 2^h (e.g. 2^5 = 32) to find the network ID of the following subnet
add 32 each time to find each subnet
Define public addresses
used in networks accessible on the internet
Define private addresses
used in internal networks - not routable on the internet
What does the NAT do
translates a private IPv4 address to a public address
What is ICMP
is a L3 supporting protocol
