Subnetting

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
technology/networking/subnet_cheatsheet.txt · Last modified: 2015/10/20 19:40 by travis
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