IPv4 Cheat Sheet
CIDR SUBNET MASK CHEATSHEET, ICMP TYPE CODES & EXTREME NUMBERS
Netmask Netmask (binary) CIDR Notes
_____________________________________________________________________________
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
To delegate rDNS cidr blocks see: http://www.rfc-editor.org/rfc/rfc2317.txt
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Note: Some allocations may be outdated
Net Host Total
Net Addr Addr Addr Number
Class Range NetMask Bits Bits of hosts
----------------------------------------------------------
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 )
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
List of special use prefixes:
0.0.0.0/8
127.0.0.0/8
192.0.2.0/24
10.0.0.0/8
172.16.0.0/12
192.168.0.0/16
169.254.0.0/16
all D/E space
(ref: RFC1918 http://www.rfc-editor.org/rfc/rfc1918.txt )
(rfc search: http://www.rfc-editor.org/rfcsearch.html )
( http://www.ietf.org/ietf/1id-abstracts.txt )
filtered source addresses
0/8 ! broadcast
10/8 ! RFC 1918 private
127/8 ! loopback
169.254.0/16 ! link local
172.16.0.0/12 ! RFC 1918 private
192.0.2.0/24 ! TEST-NET
192.168.0/16 ! RFC 1918 private
224.0.0.0/4 ! class D multicast
240.0.0.0/5 ! class E reserved
248.0.0.0/5 ! reserved
255.255.255.255/32 ! broadcast
----------------------------------------------------------
well known ports: (rfc1700.txt)
http://www.iana.org/assignments/port-numbers
protocol numbers:
http://www.iana.org/assignments/protocol-numbers
http://www.iana.org/numbers.htm
ICMP(Types/Codes)
Testing Destination Reachability & Status
(0/0) Echo-Reply
(8/0) Echo
Unreachable Destinations
(3/0) Network Unreachable
(3/1) Host Unreachable
(3/2) Protocol Unreachable
(3/3) Port Unreachable
(3/4) Fragmentaion Needed and DF set (Pkt too big)
(3/5) Source Route Failed
(3/6) Network Unknown
(3/7) Host Unknown
(3/9) DOD Net Prohibited
(3/10) DOD Host Prohibited
(3/11) Net TOS Unreachable
(3/12) Host TOS Unreachable
(3/13) Administratively Prohibited
(3/14) Host Precedence Unreachable
(3/15) Precedence Unreachable
Flow Control
(4/0) Source-Quench [RFC 1016]
Route Change Requests from Gateways
(5/0) Redirect Datagrams for the Net
(5/1) Redirect Datagrams for the Host
(5/2) Redirect Datagrams for the TOS and Net
(5/3) Redirect Datagrams for the TOS and Host
Router
(6/-) Alternate-Address
(9/0) Router-Advertisement
(10/0) Router-Solicitation
Detecting Circular or Excessively Long Routes
(11/0) Time to Live Count Exceeded
(11/1) Fragment Reassembly Time Exceeded
Reporting Incorrect Datagram Headers
(12/0) Parameter-Problem
(12/1) Option Missing
(12/2) No Room for Option
Clock Synchronization and Transit Time Estimation
(13/0) Timestamp-Request
(14/0) Timestamp-Reply
Obtaining a Network Address (RARP Alternative)
(15/0) Information-Request
(16/0) Information-Reply
Obtaining a Subnet Mask [RFC 950]
(17/0) Address Mask-Request
(18/0) Address Mask-Reply
Other
(30/0) Traceroute
(31/0) Conversion-Error
(32/0) Mobile-Redirect
Ref: [RFC 792] [RFC 896] [RFC 950] [RFC 1016]
Extreme Number Cheatsheet (for those having to deal with such quantities)
Le Système International d'Unités (SI) Decimal system Prefix's
Factor Exponent Prefix Symbol
----------------------------------------------------------------------------
1 000 000 000 000 000 000 000 000 000 000 000 000 10^36 ..(undefined) U*
1 000 000 000 000 000 000 000 000 000 000 000 10^33 .... vendeka* V*
1 000 000 000 000 000 000 000 000 000 000 10^30 ....... weka* W*
1 000 000 000 000 000 000 000 000 000 10^27 ...... xenna* X*
1 000 000 000 000 000 000 000 000 10^24 ...... yotta Y
1 000 000 000 000 000 000 000 10^21 ...... zetta Z
1 000 000 000 000 000 000 10^18 ........ exa E
1 000 000 000 000 000 10^15 ....... peta P
1 000 000 000 000 10^12 ....... tera T
1 000 000 000 10^9 ........ giga G
1 000 000 10^6 ........ mega M
1 000 10^3 ........ kilo k
100 10^2 ....... hecto h
10 10^1 ........ deka da
0.1 10^-1 ....... deci d
0.01 10^-2 ...... centi c
0.001 10^-3 ...... milli m
0.000 001 10^-6 ...... micro µ
0.000 000 001 10^-9 ....... nano n
0.000 000 000 001 10^-12 ...... pico p
0.000 000 000 000 001 10^-15 ..... femto f
0.000 000 000 000 000 001 10^-18 ...... atto a
0.000 000 000 000 000 000 001 10^-21 ..... zepto z
0.000 000 000 000 000 000 000 001 10^-24 ..... yocto y
0.000 000 000 000 000 000 000 000 001 10^-27 ..... xenno* x*
0.000 000 000 000 000 000 000 000 000 001 10^-30 ...... weko* w*
0.000 000 000 000 000 000 000 000 000 000 001 10^-33 ... vendeko* v*
0.000 000 000 000 000 000 000 000 000 000 000 001 10^-36 .(undefined) u*
----------------------------------------------------------------------------
[... 000 000 000 000 000 000 000 000 000 000 ...] 10^100 .... googol*
[... 000 000 000 000 000 000 000 000 000 000 ...] 10^googol . googolplex*
google = 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
----------------------------------------------------------------------------
(unofficial*)
note: The term "googol" was made up by a nephew of American mathematician Edward Kasner
when Kasner asked him to create a name for a very large number
CERT® Coordination Center
Intruder Detection Checklist
http://web.archive.org/web/20080109214340/http://www.cert.org/tech_tips/intruder_detection_checklist.html
Convert Fahrenheit <> Celsius:
Celsius = (Fahrenheit - 32) / 1.8
Fahrenheit = (Celsius * 1.8) + 32
One therm = 100,000 BTU = 29.29 Kw/hr = 29290 Watts
last updated: 19Jan2010
next update: 2011
original published (c)1990,(c)1991 P.E.G. Laboratories
original drafted 1985 by T.E. @ the NASA Telemetry Groundstation, Moffett Field, CA
original web publishing 08dec1992 P.E.G. Laboratories http://peglabs.com
OK to reproduce in entirety only