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 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 ) ---------------------------------------------------------- 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 ---------------------------------------------------------- well known ports: (rfc1700.txt) www.iana.org/assignments/port-numbers protocol numbers: www.iana.org/assignments/protocol-numbers 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] www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_5_3/cofigide/qos.htm#19774 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 --------------------------------------------------- Convert Fahrenheit <> Celsius: Celsius = (Fahrenheit - 32) / 1.8 Fahrenheit = (Celsius * 1.8) + 32 last updated: 4jul02