What does this Computer Networks cheat sheet cover?

It has 10 sections: Layers, HTTP, DNS, Transport, TCP, IP/Subnetting, Routing, Ethernet, NAT/DHCP and Security. Together they cover the topics a typical Computer Networks exam tests, including OSI and TCP/IP layers, HTTP and DNS, TCP vs UDP and TCP handshake and congestion control.

Is the computer networking cheat sheet free?

The first part is free to read on this page, with no account needed. The full sheet opens in the app with Unlimited ($4.99 a month or $19 for a semester), where you can edit it, print it or save it as a PDF. It is one US Letter page and prints cleanly in black and white or colour.

Can I bring this Computer Networks cheat sheet to my exam?

Only if your course allows a note sheet, so check the syllabus. This one is a single US Letter page. If your exam allows a different size, such as a 3x5 or 4x6 index card or one page front and back, Cheat Sheet AI makes one at exactly that size from your own lecture notes.

The sheet was written by our engine from a standard course outline, then a second model fact-checked every formula and statement against it; it corrected 2 statements before publishing. Notation and emphasis vary between courses, so check it against your own lecture notes.

Can I make a Computer Networks sheet from my own notes?

Yes. Upload your lecture slides, notes or study guide and Cheat Sheet AI writes a sheet in your course's notation, sized to exactly the space your exam allows. Your first sheets are free.

ComputingComputer Networks

Computer Networking Cheat Sheet — 1-page PDF

OSI/TCP-IP layers, HTTP/DNS, TCP/UDP, IP/subnetting, routing, Ethernet/NAT/DHCP, security. The whole course on one dense, printable page for your midterm or final, with every formula typeset and worked examples where they help.

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For a specific exam: Computer Networks Final exam study sheet.

1 pageUS Letter
10 sections9 topics
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Preview of the one-page Computer Networks cheat sheet: OSI/TCP-IP layers, HTTP/DNS, TCP/UDP, IP/subnetting, routing, Ethernet/NAT/DHCP, security — the whole course, one page

On the sheet

What’s on it

The topics a typical Computer Networks exam tests, all on the one page.

OSI and TCP/IP layers
HTTP and DNS
TCP vs UDP
TCP handshake and congestion control
IP addressing and subnetting
Routing algorithms
ARP and Ethernet
NAT and DHCP
Network security basics

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The free part, as text

The free part of the sheet, section by section. Unlock the full sheet to read the rest, edit any block, and print it or save it as a PDF.

01Layers

OSI vs TCP/IP

OSI layer	TCP/IP	Main PDU / func
7 App	App	msg; HTTP, DNS, SMTP
6 Pres	App	format, encrypt, compress
5 Sess	App	dialog control
4 Trans	Transport	segment/datagram; TCP, UDP
3 Net	Internet	packet; IP, routing
2 Data link	Link	frame; MAC, ARP, Ethernet
1 Phys	Link	bits; media, signaling

Encapsulation: App data + headers/trailers added at each layer: $m s g \to segment \to packet \to frame \to bits$ .
PDU: Protocol data unit: app $m s g$ , TCP $segment$ , IP $packet$ , link $frame$ , phys $bits$ .

End host: app + transport + IP + link + physical
Router: IP + link + physical
Switch: link + physical

Watch out:Layer names differ by model; exam usually maps the $O S I$ $7$ -layer model to a $T C P / I P$ $5$ -layer stack by splitting link into data-link + physical.

02DNS

Record types

Type	Meaning
A	name $\to$ IPv4
AAAA	name $\to$ IPv6
NS	authoritative server
CNAME	alias to canonical name
MX	mail exchanger

Stub resolver asks local recursive resolver
Recursive resolver queries root $\to$ TLD $\to$ authoritative
Result cached using TTL

Caching

TTL = time to live; cached DNS answer valid until TTL expires

reduces lookup delay and traffic

Watch out:DNS lookup may be cached at host, resolver, or browser; stale answer possible until TTL expires.

03Transport

TCP vs UDP

Property	TCP	UDP
Connection	connection-oriented	connectionless
Reliability	yes	no
Ordering	in-order byte stream	no guarantee
Flow/congestion ctrl	yes	no
Header size	20+ B	8 B
Use	web, mail, file transfer	DNS, streaming, VoIP

04TCP

Slow start: cwnd grows exponentially per RTT
Congestion avoidance: cwnd grows linearly
Fast retransmit: 3 duplicate ACKs $\Rightarrow$ loss suspected
Fast recovery: reduce cwnd, avoid full slow start

Watch out:TCP ACKs are cumulative; one ACK can confirm many bytes. Duplicate ACKs often indicate a missing segment.

05IP/Subnetting

IPv4: $32$ -bit address, written as $4$ dotted decimal octets.

Hosts/subnet

usable hosts = 2^{h} - 2

usual IPv4 subnet with $h$ host bits; subtract network and broadcast addresses

Prefix

subnet mask $= / n \Rightarrow n$ network bits, $32 - n$ host bits

CIDR notation

Network address

network = IP & mask

bitwise AND

Broadcast address

broadcast = network $∣$ host bits all 1

IPv4 subnet broadcast

06Ethernet

Ethernet frame: Data-link PDU with destination MAC, source MAC, type/length, payload, FCS.

FCS

FCS = CRC over frame

error detection in Ethernet

ARP: Resolves IPv4 address $\to$ MAC address on local link.

Host checks ARP cache
Broadcast ARP request: "Who has $IP$ ?"
Owner replies unicast with MAC
Cache entry stored for a while

Watch out:ARP works only within a LAN/broadcast domain; routers do not forward ARP broadcasts.

Ex.Send to remote host: need destination MAC?

Yes, but only of the next hop (default gateway), not the final remote IP host.

07NAT/DHCP

NAT: Network Address Translation: rewrites IP/port fields so many private hosts share one public IP.

Private IPv4 ranges

Range	Use
$10.0.0.0/8$	large private net
$172.16.0.0/12$	medium private net
$192.168.0.0/16$	small private net

Cheat sheet locked

Also on the full Computer Networks sheet

9 more sections, with every definition, formula and worked example. Unlimited unlocks every full sheet in the library to edit, print or save as a PDF, and makes unlimited sheets from your own notes.

HTTP

HTTP
Common methods
Status classes
Persistent conn

DNS

Transport

Port
TCP socket
Multiplexing
Demultiplexing

TCP

3-way handshake
Sequence number
ACK number
Timeout/Retransmit
Flow vs congestion
Send window

IP/Subnetting

IPv6

Routing

Routing table
Algorithms
Shortest path
DV update
Metric

Ethernet

MAC address

NAT/DHCP

PAT
DHCP

Security

Threats
Confidentiality
Integrity
Authentication
Availability
TLS role

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FAQ

Questions

About the Computer Networks sheet and making your own.

What does this Computer Networks cheat sheet cover?: It has 10 sections: Layers, HTTP, DNS, Transport, TCP, IP/Subnetting, Routing, Ethernet, NAT/DHCP and Security. Together they cover the topics a typical Computer Networks exam tests, including OSI and TCP/IP layers, HTTP and DNS, TCP vs UDP and TCP handshake and congestion control.
Is the computer networking cheat sheet free?: The first part is free to read on this page, with no account needed. The full sheet opens in the app with Unlimited ($4.99 a month or $19 for a semester), where you can edit it, print it or save it as a PDF. It is one US Letter page and prints cleanly in black and white or colour.
Can I bring this Computer Networks cheat sheet to my exam?: Only if your course allows a note sheet, so check the syllabus. This one is a single US Letter page. If your exam allows a different size, such as a 3x5 or 4x6 index card or one page front and back, Cheat Sheet AI makes one at exactly that size from your own lecture notes.
How accurate is it?: The sheet was written by our engine from a standard course outline, then a second model fact-checked every formula and statement against it; it corrected 2 statements before publishing. Notation and emphasis vary between courses, so check it against your own lecture notes.
Can I make a Computer Networks sheet from my own notes?: Yes. Upload your lecture slides, notes or study guide and Cheat Sheet AI writes a sheet in your course's notation, sized to exactly the space your exam allows. Your first sheets are free.

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