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Network+ | 6.1. IPv4 Cheat Sheet by

CompTIA Network+ certification course sum up. Oriented for cybersecurity later courses.

Layers

@Layer2
btw 2 devices inside own NW or LAN
@Layer3
btw 2 NWs or 2 subnets

IPv4

Notation
dotted­-de­cimal | 4x8bits = 32bits
Subnet mask
defines NW proportion (1=NW, 0=host)
Classes
classful mask = default subnet mask
- Class A
1-126
255.0.0.0
/8
- Class B
128-191
255.25­5.0.0
/16
- Class C
192-223
255.25­5.255.0
/24
- Class D
224-239
n/a
n/a
 
IP Types
- Routable
Public IPs purchased and used by ISP
- Private
non routable
 
A
10.0.0.0/8
10.255.25­5.255/8
 
B
172.16.0.0/16
172.31.25­5.2­55/16
 
C
192.16­8.0.0/24
192.16­8.2­55.2­55/24
- Specia­lized
127.x.x.x
loopback adress for local testing
- Automatic
APIPA
assigned by OS if DHCP u/s
- Virtual
VIP(A)
not correl­ating to any NIC
 
ex @L7: loadba­lancer, failover
 
ex @L3: HSRP (Hot StandBy Routing Prot.)

IPv4 Data flows

Unicast
single destin­ation
Multicast
multi-­spe­cific destin­ation
Broadcast
all devices on a network

Assignment

Static
simple, time-c­ons­uming, prone to error, hard to setup in large scale
Dynamic
quick, easy, scalable
Content
IP adress, subnet mask, default GW, DNS server (or WINS)
TTL
time for which an IP is leased to a host. After, IP is given back to IP pool
APIPA
IP self-a­ssigned in case of DHCP unavai­lable, from the network 169.25­4.0.0/16
ZeroConf
idem but more recent, using mDNS and DNS-SD
 

Subnet masks and available IPs

Subnetting

Purpose
scaling NW according to its scope of use, to control bandwidth
How
borrow bits from original host portion and add them to the NW portion
Calcul­ation
IP
10.
180.
122.
244
/13
Mask
255.
248.
0.
0
256-248 = 8 hots/s­ubnet | 180%8 = 4 | 180-4 = 176
Subnet
10.
176.
0.
0
the next subnet is 176+8=184
Brdcst
10.
183.
255.
255
1st IP
10.
176.
0.
1
Last IP
10.
183.
255.
254
       
 

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  • Published: 28th March, 2023

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