Network Cheatsheet
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Netmask Netmask (binary) CIDR Notes
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255.255.255.255 11111111.11111111.11111111.11111111 /32 Host (single addr)
255.255.255.254 11111111.11111111.11111111.11111110 /31 Unuseable
255.255.255.252 11111111.11111111.11111111.11111100 /30 2 useable
255.255.255.248 11111111.11111111.11111111.11111000 /29 6 useable
255.255.255.240 11111111.11111111.11111111.11110000 /28 14 useable
255.255.255.224 11111111.11111111.11111111.11100000 /27 30 useable
255.255.255.192 11111111.11111111.11111111.11000000 /26 62 useable
255.255.255.128 11111111.11111111.11111111.10000000 /25 126 useable
255.255.255.0 11111111.11111111.11111111.00000000 /24 "Class C" 254 useable
255.255.254.0 11111111.11111111.11111110.00000000 /23 2 Class C's
255.255.252.0 11111111.11111111.11111100.00000000 /22 4 Class C's
255.255.248.0 11111111.11111111.11111000.00000000 /21 8 Class C's
255.255.240.0 11111111.11111111.11110000.00000000 /20 16 Class C's
255.255.224.0 11111111.11111111.11100000.00000000 /19 32 Class C's
255.255.192.0 11111111.11111111.11000000.00000000 /18 64 Class C's
255.255.128.0 11111111.11111111.10000000.00000000 /17 128 Class C's
255.255.0.0 11111111.11111111.00000000.00000000 /16 "Class B"
255.254.0.0 11111111.11111110.00000000.00000000 /15 2 Class B's
255.252.0.0 11111111.11111100.00000000.00000000 /14 4 Class B's
255.248.0.0 11111111.11111000.00000000.00000000 /13 8 Class B's
255.240.0.0 11111111.11110000.00000000.00000000 /12 16 Class B's
255.224.0.0 11111111.11100000.00000000.00000000 /11 32 Class B's
255.192.0.0 11111111.11000000.00000000.00000000 /10 64 Class B's
255.128.0.0 11111111.10000000.00000000.00000000 /9 128 Class B's
255.0.0.0 11111111.00000000.00000000.00000000 /8 "Class A"
254.0.0.0 11111110.00000000.00000000.00000000 /7
252.0.0.0 11111100.00000000.00000000.00000000 /6
248.0.0.0 11111000.00000000.00000000.00000000 /5
240.0.0.0 11110000.00000000.00000000.00000000 /4
224.0.0.0 11100000.00000000.00000000.00000000 /3
192.0.0.0 11000000.00000000.00000000.00000000 /2
128.0.0.0 10000000.00000000.00000000.00000000 /1
0.0.0.0 00000000.00000000.00000000.00000000 /0 IP space
For wildcard netmasks (aka reverse netmasks), subtract each octet of a standard netmask from 255.
Example 1: 255.255.255.0 becomes 0.0.0.255
Example 2: 255.255.252.0 becomes 0.0.3.255
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Net Host Total
Net Addr Addr Addr Number
Class Range NetMask Bits Bits of hosts
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A 0-127 255.0.0.0 8 24 16777216 (i.e. 114.0.0.0)
B 128-191 255.255.0.0 16 16 65536 (i.e. 150.0.0.0)
C 192-254 255.255.255.0 24 8 256 (i.e. 199.0.0.0)
D 224-239 (multicast)
E 240-255 (reserved)
F 208-215 255.255.255.240 28 4 16
G 216/8 ARIN - North America
G 217/8 RIPE NCC - Europe
G 218-219/8 APNIC
H 220-221 255.255.255.248 29 3 8 (reserved)
K 222-223 255.255.255.254 31 1 2 (reserved)
(ref: RFC1375 & http://www.iana.org/assignments/ipv4-address-space )
( http://www.iana.org/numbers.htm )
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* Reserved IP Addresses
Private Network Address Ranges
IP Range # Addresses
10.0.0.0/8 16,777,216
172.16.0.0/12 1,048,576
192.168.0.0/16 65,536
Local Address Ranges
IP Range # Addresses Notes
0.0.0.0/8 16,777,216 For broadcast messages to current network
127.0.0.0/8 16,777,216 For loopback addresses to local host
169.254.0.0/16 65,536 For autoconfiguration between 2 hosts on a single link
Address Ranges for Documentation and Example Code
IP Range # Addresses
192.0.2.0/24 256
198.51.100.0/24 256
203.0.113.0/24 256
Special-Purpose Address Ranges
IP Range # Addresses Notes
100.64.0.0/10 4,194,304 New in 2012! For carrier-grade NAT, but may be used for private networks
192.0.0.0/29 8 For DS-Lite transition mechanism
192.88.99.0/24 256 For 6to4 anycast relays
198.18.0.0/15 131,072 For benchmark tests of routers
224.0.0.0/4 268,435,456 For multicast
240.0.0.0/4 268,435,455 For future use
255.255.255.255/32 1 For limited broadcast
See https://tools.ietf.org/html/rfc5735 (covers 15 of the 16 reserved networks)
See https://tools.ietf.org/html/rfc6598 (covers the new kid on the block, 100.64.0.0/10)
See http://en.wikipedia.org/wiki/Reserved_IP_addresses
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* Martians: (updates at: www.iana.org/assignments/ipv4-address-space )
http://en.wikipedia.org/wiki/Martian_packet
http://en.wikipedia.org/wiki/Bogon_filtering
no ip source-route
access-list 100 deny ip host 0.0.0.0 any
deny ip 0.0.0.0 0.255.255.255 any log ! antispoof
deny ip 0.0.0.0 0.255.255.255 0.0.0.0 255.255.255.255 ! antispoof
deny ip any 255.255.255.128 0.0.0.127 ! antispoof
deny ip host 0.0.0.0 any log ! antispoof
deny ip host [router intf] [router intf] ! antispoof
deny ip xxx.xxx.xxx.0 0.0.0.255 any log ! lan area
deny ip 0/8 0.255.255.255 any log ! IANA - Reserved
deny ip 1/8 0.255.255.255 any log ! IANA - Reserved
deny ip 2/8 0.255.255.255 any log ! IANA - Reserved
deny ip 5/8 0.255.255.255 any log ! IANA - Reserved
deny ip 7/8 0.255.255.255 any log ! IANA - Reserved
deny ip 10.0.0.0 0.255.255.255 any log ! IANA - Private Use
deny ip 23/8 0.255.255.255 any log ! IANA - Reserved
deny ip 27/8 0.255.255.255 any log ! IANA - Reserved
deny ip 31/8 0.255.255.255 any log ! IANA - Reserved
deny ip 36-37/8 0.255.255.255 any log ! IANA - Reserved
deny ip 39/8 0.255.255.255 any log ! IANA - Reserved
deny ip 41-42/8 0.255.255.255 any log ! IANA - Reserved
deny ip 50/8 0.255.255.255 any log ! IANA - Reserved
deny ip 58-60/8 0.255.255.255 any log ! IANA - Reserved
deny ip 69-79/8 0.255.255.255 any log ! IANA - Reserved
deny ip 82-95/8 0.255.255.255 any log ! IANA - Reserved
deny ip 96-126/8 0.255.255.255 any log ! IANA - Reserved
deny ip 127/8 0.255.255.255 any log ! IANA - Reserved
deny ip 169.254.0.0 0.0.255.255 any log ! link-local network
deny ip 172.16.0.0 0.15.255.255 any log ! reserved
deny ip 192.168.0.0 0.0.255.255 any log ! reserved
deny ip 192.0.2.0 0.0.0.255 any log ! test network
deny ip 197/8 0.255.255.255 any log ! IANA - Reserved
deny ip 220/8 0.255.255.255 any log ! IANA - Reserved
deny ip 222-223/8 0.255.255.255 any log ! IANA - Reserved
deny ip 224.0.0.0 31.255.255.255 any log ! multicast
deny ip 224.0.0.0 15.255.255.255 any log ! unless MBGP-learned routes
deny ip 224-239/8 0.255.255.255 any log ! IANA - Multicast
deny ip 240-255/8 0.255.255.255 any log ! IANA - Reserved
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* IP Address Blocks ARIN Issues From (https://www.arin.net/knowledge/ip_blocks.html)
23.0.0.0/8
24.0.0.0/8
50.0.0.0/8
63.0.0.0/8
64.0.0.0/8
65.0.0.0/8
66.0.0.0/8
67.0.0.0/8
68.0.0.0/8
69.0.0.0/8
70.0.0.0/8
71.0.0.0/8
72.0.0.0/8
73.0.0.0/8
74.0.0.0/8
75.0.0.0/8
76.0.0.0/8
96.0.0.0/8
97.0.0.0/8
98.0.0.0/8
99.0.0.0/8
100.0.0.0/8
104.0.0.0/8
107.0.0.0/8
108.0.0.0/8
135.0.0.0/8
136.0.0.0/8
142.0.0.0/8
147.0.0.0/8
162.0.0.0/8
166.0.0.0/8
172.0.0.0/8
173.0.0.0/8
174.0.0.0/8
192.0.0.0/8
198.0.0.0/8
199.0.0.0/8
204.0.0.0/8
205.0.0.0/8
206.0.0.0/8
207.0.0.0/8
208.0.0.0/8
209.0.0.0/8
216.0.0.0/8
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* Well known ports: (rfc1700.txt)
www.iana.org/assignments/port-numbers
protocol numbers:
www.iana.org/assignments/protocol-numbers
www.iana.org/numbers.htm
Protocol Protocol Number
-------- ---------------
ICMP 1
IGRP 9
EIGRP 88
OSPF 89
IPv6 41
GRE 47
IPX in IP 111
L2TP 115
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* Wireless (See http://en.wikipedia.org/wiki/IEEE_802.11)
Protocol Year Frequency Data Rate per stream Allowable # Streams Indoor Range Outdoor Range
- 1997 2.4 GHz 1-2 Mb/s 1 stream 66 feet 330 feet
a 1999 5 GHz 6-54 Mb/s 1 stream 115 feet 380 feet
b 1999 2.4 GHz 1-11 Mb/s 1 stream 115 feet 460 feet
g 2003 2.4 GHz 6-54 Mb/s 1 stream 125 feet 460 feet
n 2009 2.4/5 GHz 7-150 Mb/s 4 streams 230 feet 820 feet
ac 2012 5 GHz max 867 Mb/s 8 streams ? ?
ad 2014 2.4/5/60 GHz ? ? ? ?
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