The document discusses CIDR (Classless Inter-Domain Routing) notation, which is used to represent IP addresses and routing prefixes in a compact format. CIDR notation specifies the IP address followed by a slash and the routing prefix size. This allows the representation of both single IP addresses and entire networks. The number of addresses within a subnet is calculated using the prefix size, with larger prefixes encompassing more addresses. Examples are provided of common CIDR prefix sizes and their resulting subnet sizes and address ranges.

1. AWS - VPC (Virtual
Private Cloud)
VPC ADDRESSING - CIDR
federico.panini@fazland.com - CTO

2. federico.panini@fazland.com - CTO
CIDR Notation is a compact representation of an IP
address and its own routing prefix. The notation is
build with the ip address and the routing prefix
equivalent to the number or leading 1-bits in the
routing prefix mask.
This notation is used either for IPv4 and IPv6. The IP is
followed by a slash character “/” and then the routing
prefix. The address may identify a single IP address or
the beginning of an entire network.
AWS - VPC Addressing
basic concepts - vpc addressing - CIDR
192.168.1.129/24

3. AWS - VPC Addressing
basic concepts - vpc addressing - CIDR
federico.panini@fazland.com - CTO
The number of addresses of a subnet defined by the
prefix can be calculated as:
192.168.1.129/24 = 2^32-24 = 2^8 = 256 addr.
2 address size - prefix size
192.168.1.129/16 = 2^32-16 = 2^16 = 65536 addr.
192.168.1.129/8 = 2^32-8 = 2^24 = 16,777,216 addr.
192.168.1.129/32 = 2^32-32 = 2^0 = 1 addr.

4. federico.panini@fazland.com - CTO
AWS - VPC Addressing
basic concepts - vpc addressing - CIDR
IP/CIDR Δ to last IP addrMask Hosts (*) Size Restrictions on a/b/c/d
a.b.c.d/32 +0.0.0.0 255.255.255.255 1 1/256 C
a.b.c.d/31 +0.0.0.1 255.255.255.254 2 1/128 C d = 0 ... (2n) ... 254
a.b.c.d/30 +0.0.0.3 255.255.255.252 4 1/64 C d = 0 ... (4n) ... 252
a.b.c.d/29 +0.0.0.7 255.255.255.248 8 1/32 C d = 0 ... (8n) ... 248
a.b.c.d/28 +0.0.0.15 255.255.255.240 16 1/16 C d = 0 ... (16n) ... 240
a.b.c.d/27 +0.0.0.31 255.255.255.224 32 ⅛ C d = 0 ... (32n) ... 224
a.b.c.d/26 +0.0.0.63 255.255.255.192 64 ¼ C d = 0, 64, 128, 192
a.b.c.d/25 +0.0.0.127 255.255.255.128 128½ C d = 0, 128
a.b.c.0/24 +0.0.0.255 255.255.255.000 2561 C
CLASS C

5. AWS - VPC Addressing
basic concepts - vpc addressing - CIDR
federico.panini@fazland.com - CTO
IP/CIDR Δ to last IP addrMask Hosts (*) Size Restrictions on a/b/c/d
a.b.c.0/23 +0.0.1.255 255.255.254.000 5122 C c = 0 ... (2n) ... 254
a.b.c.0/22 +0.0.3.255 255.255.252.000 1,024 4 C c = 0 ... (4n) ... 252
a.b.c.0/21 +0.0.7.255 255.255.248.000 2,048 8 C c = 0 ... (8n) ... 248
a.b.c.0/20 +0.0.15.255255.255.240.000 4,096 16 C c = 0 ... (16n) ... 240
a.b.c.0/19 +0.0.31.255255.255.224.000 8,192 32 C c = 0 ... (32n) ... 224
a.b.c.0/18 +0.0.63.255255.255.192.000 16,384 64 C c = 0, 64, 128, 192
a.b.c.0/17 +0.0.127.255 255.255.128.000 32,768 128 C c = 0, 128
a.b.0.0/16 +0.0.255.255 255.255.000.000 65,536 256 C = 1 B
CLASS A

6. AWS - VPC Addressing
basic concepts - vpc addressing - CIDR
federico.panini@fazland.com - CTO
IP/CIDR Δ to last IP addrMask Hosts (*) Size Restrictions on a/b/c/d
a.b.0.0/15 +0.1.255.255 255.254.000.000 131,072 2 B b = 0 ... (2n) ... 254
a.b.0.0/14 +0.3.255.255 255.252.000.000 262,144 4 B b = 0 ... (4n) ... 252
a.b.0.0/13 +0.7.255.255 255.248.000.000 524,288 8 B b = 0 ... (8n) ... 248
a.b.0.0/12 +0.15.255.255 255.240.000.000 1,048,576 16 B b = 0 ... (16n) ... 240
a.b.0.0/11 +0.31.255.255 255.224.000.000 2,097,152 32 B b = 0 ... (32n) ... 224
a.b.0.0/10 +0.63.255.255 255.192.000.000 4,194,304 64 B b = 0, 64, 128, 192
a.b.0.0/9 +0.127.255.255 255.128.000.000 8,388,608 128 B b = 0, 128
a.0.0.0/8 +0.255.255.255 255.000.000.000 16,777,216 256 B = 1 A
CLASS A

7. AWS - VPC Addressing
basic concepts - vpc addressing - CIDR
federico.panini@fazland.com - CTO
IP/CIDR Δ to last IP addrMask Hosts (*) Size Restrictions on a/b/c/d
a.0.0.0/7 +1.255.255.255 254.000.000.000 33,554,432 2 A a = 0 ... (2n) ... 254
a.0.0.0/6 +3.255.255.255 252.000.000.000 67,108,864 4 A a = 0 ... (4n) ... 252
a.0.0.0/5 +7.255.255.255 248.000.000.000 134,217,728 8 A a = 0 ... (8n) ... 248
a.0.0.0/4 +15.255.255.255 240.000.000.000 268,435,456 16 A a = 0 ... (16n) ... 240
a.0.0.0/3 +31.255.255.255 224.000.000.000 536,870,912 32 A a = 0 ... (32n) ... 224
a.0.0.0/2 +63.255.255.255 192.000.000.000 1,073,741,824 64 A a = 0, 64, 128, 192
a.0.0.0/1 +127.255.255.255 128.000.000.000 2,147,483,648 128 A a = 0, 128
0.0.0.0/0 +255.255.255.255 000.000.000.000 4,294,967,296 256 A

8. AWS - VPC Addressing
basic concepts - vpc addressing - CIDR
• http://docs.aws.amazon.com/AmazonVPC/latest/GettingStartedGuide/
ExerciseOverview.html
• http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing
federico.panini@fazland.com - CTO