Network Cheatsheet
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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
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
----------------------------------------------------------
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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The current 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 )
( or ftp://ftp.isi.edu/in-notes/rfc1918.txt )
(rfc search: http://www.rfc-editor.org/rfcsearch.html )
( http://www.ietf.org/ietf/1id-abstracts.txt )
( http://www.ietf.org/shadow.html )
Martians: (updates at: www.iana.org/assignments/ipv4-address-space )
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
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
ARIN administrated blocks: (http://www.arin.net/regserv/IPStats.html)
24.0.0.0/8 (portions of)
63.0.0.0/8
64.0.0.0/8
65.0.0.0/8
66.0.0.0/8
196.0.0.0/8
198.0.0.0/8
199.0.0.0/8
200.0.0.0/8
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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* ICMP Type Numbers
Type Name Reference
---- ------------------------- ---------
0 Echo Reply [RFC792]
Codes
0 No Code
1 Unassigned [JBP]
2 Unassigned [JBP]
3 Destination Unreachable [RFC792]
Codes
0 Net Unreachable
1 Host Unreachable
2 Protocol Unreachable
3 Port Unreachable
4 Fragmentation Needed and Don't Fragment was Set
5 Source Route Failed
6 Destination Network Unknown
7 Destination Host Unknown
8 Source Host Isolated
9 Communication with Destination Network is
Administratively Prohibited
10 Communication with Destination Host is
Administratively Prohibited
11 Destination Network Unreachable for Type of Service
12 Destination Host Unreachable for Type of Service
13 Communication Administratively Prohibited [RFC1812]
14 Host Precedence Violation [RFC1812]
15 Precedence cutoff in effect [RFC1812]
4 Source Quench [RFC792]
Codes
0 No Code
5 Redirect [RFC792]
Codes
0 Redirect Datagram for the Network (or subnet)
1 Redirect Datagram for the Host
2 Redirect Datagram for the Type of Service and Network
3 Redirect Datagram for the Type of Service and Host
6 Alternate Host Address [JBP]
Codes
0 Alternate Address for Host
7 Unassigned [JBP]
8 Echo [RFC792]
Codes
0 No Code
9 Router Advertisement [RFC1256]
Codes
0 Normal router advertisement
16 Does not route common traffic [RFC2002]
10 Router Selection [RFC1256]
Codes
0 No Code
11 Time Exceeded [RFC792]
Codes
0 Time to Live exceeded in Transit
1 Fragment Reassembly Time Exceeded
12 Parameter Problem [RFC792]
Codes
0 Pointer indicates the error
1 Missing a Required Option [RFC1108]
2 Bad Length
13 Timestamp [RFC792]
Codes
0 No Code
14 Timestamp Reply [RFC792]
Codes
0 No Code
15 Information Request [RFC792]
Codes
0 No Code
16 Information Reply [RFC792]
Codes
0 No Code
17 Address Mask Request [RFC950]
Codes
0 No Code
18 Address Mask Reply [RFC950]
Codes
0 No Code
19 Reserved (for Security) [Solo]
20-29 Reserved (for Robustness Experiment) [ZSu]
30 Traceroute [RFC1393]
31 Datagram Conversion Error [RFC1475]
32 Mobile Host Redirect [David Johnson]
33 IPv6 Where-Are-You [Bill Simpson]
34 IPv6 I-Am-Here [Bill Simpson]
35 Mobile Registration Request [Bill Simpson]
36 Mobile Registration Reply [Bill Simpson]
39 SKIP [Markson]
40 Photuris [RFC2521]
Codes
0 = Bad SPI
1 = Authentication Failed
2 = Decompression Failed
3 = Decryption Failed
4 = Need Authentication
5 = Need Authorization
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]
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Decimal system Prefix's
Factor Exponent Prefix
---------------------------------------------------
1 000 000 000 000 000 000 000 000...10^24....yotta
1 000 000 000 000 000 000 000...10^21....zetta
1 000 000 000 000 000 000...10^18....exa
1 000 000 000 000 000...10^15....peta
1 000 000 000 000...10^12....tera
1 000 000 000...10^9.....giga
1 000 000...10^6.....mega
1 000...10^3.....kilo
100...10^2.....hecto
10...10^1.....deka
0.1...10^-1....deci
0.01...10^-2....centi
0.001...10^-3....milli
0.000 001...10^-6....micro
0.000 000 001...10^-9....nano
0.000 000 000 001...10^-12...pico
0.000 000 000 000 001...10^-15...femto
0.000 000 000 000 000 001...10^-18...atto
0.000 000 000 000 000 000 001...10^-21...zepto
0.000 000 000 000 000 000 000 001...10^-24...yocto
---------------------------------------------------
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Convert Fahrenheit <--> Celsius:
Celsius = (Fahrenheit - 32) / 1.8
Fahrenheit = (Celsius * 1.8) + 32
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