TCP/IP Basics Flashcards

1
Q

IP Packet

A

Composed at Layer 3, includes IP info and payload from Layer 4

Gets encapsulated at Layer 2

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2
Q

Internet Control Message Protocol

A

ICMP

Important role in error reporting and diagnostics

Operates at Layer 3

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3
Q

Transmission Control Protocol

A

TCP

Connection-oriented protocol

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4
Q

User Datagram Protocol

A

UDP

Connectionless protocol

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5
Q

Three way handshake

A

Part of TCP

SYN - SYN-ACK, ACK

Sender sends syn, receiver responds with syn-ack, sender sends final ack

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6
Q

Main TCP Header parts

A

Source Port - Destination Port - Sequence Number - Acknowledgement Number

Will also include:

Flags: individual bits that give info on state of connection
Checksum - recipient can use this to validate data

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7
Q

User Datagram Protocol

A

UDP

Unlike with TCP, data does not get segmented in Layer 4.

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8
Q

UDP Datagram Header

A

Source port - destination port - length - checksum

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9
Q

Universal Broadcast MAC Address

A

FF-FF-FF-FF-FF-FF

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10
Q

CLI terms to get IP and MAC on:

MacOS
WinOS
Linux

A

ifconfig
ipconfig /all
ip (or ifconfig, but that is depreciated)

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11
Q

Bits in an IP(v4) address?

A

32

4 octets

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12
Q

Network ID

A

The shared portion of clients on a LAN

client unique portions will be written as a 0

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13
Q

Default Gateway

A

IP address of the router for a LAN

Frequently will be given the lowest or highest possible IP address within the network ID range

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14
Q

Subnet mask

A

Series of ones followed by zeroes

The ones stop where the network ID stops in dotted decimal, generally.

Computers can compare their IP with another against the subnet mask - if they are identical up to where the ones stop, they share the same subnet.

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15
Q

Address Resolution Protocol

A

ARP

An ARP request broadcasts to all MAC addresses on LAN. Sends destination IP, gets a response from destination IP with corresponding destination MAC, allows NIC to create frame with destination now

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16
Q

CIDR notation

A

/[NUMBER]

Number = the number of ones in the subnet mask

Automatically know the subnet mask from CIDR notation

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17
Q

IP Class Blocks

A

Sections of IP addresses distributed out to ISPs

18
Q

Class A addresses

A

First octet 1-126

Subnet mask always 255.0.0.0

Binary always starts with 0xxxxxxx.

19
Q

Class B addresses

A

first octet 128-191

Subnet mask always 255.255.0.0

Binary always starts with 10xxxxxx.

20
Q

Class C addresses

A

first octet 192-223

Subnet always 255.255.255

Binary always starts with 110xxxxx.

21
Q

Class D addresses

A

First octet 224-239

Binary always starts with 1110xxxx.

22
Q

Class E addresses

A

First octet 240-255

Binary always starts with 1111xxxx.

23
Q

Multicast

A

Sending a packet to a group of specific computers from one source

24
Q

Anycast

A

sending a packet to the nearest computer of a pool that share the same address

25
Q

CIDR

A

Classless Interdomain routing

26
Q

Subnet Host Calculation

A

2^x - 2

x = number of 0s in the subnet mask’s binary representation

Remember - subnet masks always have 32 digits, so just subtract the /number from 32 to get your 0s.

27
Q

Available Subnet Calculation

A

Start with your Network ID and convert to binary

Then move to the right y number of digits

2^y = the number of subnets you are creating

28
Q

Manual Dotted Decimal to Binary Conversion

A

128 64 32 16 8 4 2 1

If the number in your dotted decimal is greater than the leftmost number above, subtract the left-most number from dotted decimal value. Assign a 1 to the first binary value. Take remaining value and place it above next value. If it is more, follow same process. If not, assign a 0 to the respective binary value and move on down the line.

29
Q

Convert binary to dotted decimal

A

128 64 32 16 8 4 2 1

Write the binary under each number, add the numbers that have a 1 under them.

30
Q

4 basic network assignment principles

A

1) Default gateway should get the first or last IP address in the network ID
2) Try to use IP addresses in sequential order
3) Separate servers from clients - keep servers in blocks of addresses
4) Document it all

31
Q

DHCP Server Port
DHCPS Client Port

A

UDP - 67
UDP - 68

32
Q

DHCP Scope

A

the pool of available IP addresses it can give out

33
Q

DHCP Relay

A

Feature of routers to take a DHCP client’s discovery broadcast and send it as unicast to a known DHCP server on the network

34
Q

IP Helper Address
UDP Helper Address

A

The IP address of the DHCP server given to routers so they can relay broadcasts

35
Q

IP Exclusion Range

A

A subset of IP addresses you tell the DHCP server not to assign dynamically, setting them aside for static reservation devices (printers, servers, cameras, etc.

36
Q

MAC Reservations

A

reserving IP addresses on a DHCP server using MAC addresses of clients - any time they get a request from that MAC, they know what to give already

37
Q

APIPA

A

IP in the range of 169.254.0.0/16

Automatic Private IP Addressing, happens when a DHCP server is unreachable

38
Q

DHCP Release/Renewals for:

Windows
MacOS
Linux

A

ipconfig /release
ipconfig /renew

sudo ifconfig eth0 down
sudo ifconfig eth0 up

sudo dhclient -r
sudo dhclient

39
Q

DHCP Failover

A

A pair of DHCP servers that share the same scope, provide redundancy for large enterprises

40
Q

Rogue DHCP Server

A

A DHCP server connected to the network that is handing out incorrect IP addresses and/or default gateways.

Can be used in cyberattacks

41
Q

Private IP address Blocks

A

Class A: 10.0.0.0 - 10.255.255.255
Class B: 172.16.0.0-172.31.0.0
Class C: 192.168.0.0-192.168.255.255

42
Q
A