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Siehe Hilfe:Bereichssperren/IPv6 für Informationen zu IPv6-Bereichssperren.

Bereichssperren sind technische Einschränkungen, die durch Special:Block an einer Gruppe von IP-Adressen vorgenommen werden, um diese an Bearbeitungen, Accounterstellungen, E-Mail-Versand oder anderen Aktionen zu hindern. Die Option "Sperre anwenden auf angemeldete Benutzer unter deren IP-Adresse" verhindert, dass die Sperre durch eingeloggte Benutzer umgangen werden kann.

Um einen IP-Bereich von Special:Block aus zu sperren, gib die erste IP-Adresse im Bereich ein, gefolgt von einem Schrägstrich und einem Classless inter-domain routing-Suffix (CIDR). Du solltest es vermeiden, Bereichssperren durchzuführen, es sei denn, du verstehst, was du tust, ansonsten könnten am Ende Zehntausende oder sogar Millionen von Menschen blockiert sein, die nicht das Problem sind!

Dieser Artikel behandelt hauptsächlich IPv4; IPv6-Blöcke funktionieren ähnlich, haben aber unterschiedliche Auswirkungen – siehe /IPv6.

Nicht-technische Erklärung

IP-Adressen werden in verschiedene Blöcke von Nummern aufgeteilt. Ein Beispiel hierfür wäre bis Sobald 255 erreicht, ist die nächste Zahl

IP-Adressen können in kleinere oder größere Blöcke aufgeteilt werden. Der kleinste praktischer Block ist ein 4er-Block. Dies könnte eines der Folgenden sein: -, -, -, ...

Of each block of 4 numbers, only two can be assigned to a computer. The first and last numbers of any block are reserved for network communication. These are level 30 blocks and can be expressed like this:,,, ...

The next largest block is 8. They can be as follows: -, -, -, ...

In this block of 8 numbers only 6 can be assigned to a computer as, once again, the first and last numbers in a block are reserved for specific uses in network communication. These can also be expressed as follows:,,, ...

From this point on, the number of IP addresses in a block continues to double: 16, 32, 64, 128, 256, etc.

A block of 16 would start
A block of 32 would start
A block of 64 would start
A block of 128 would start
A block of 256 would start

So if you have an IP address and you want to block the range assigned how do you know which one to use? Let's say you have a problem with You can look up who has this IP address at http://arin.net/whois/?queryinput= Say this tells us that this IP address is assigned, along with a LOT of others in a /17 range, to the Department of Defense. We certainly don't want to block a large block of the DoD! The rule of thumb is block as little as possible. Only block a range if there is a cluster of IP addresses giving a problem.

There's a calculator that is very useful for this:


Go to this site and enter into the first set of blanks. Now select Network Prefix Length and enter 27 (this will give a block of 32 addresses) and click Calculate Network Information. This will show us a block of 32 IP addresses that include (The first - network - and the last - broadcast - addresses will be displayed along with the usable addresses in the range.) You can use this tool to test ranges to be sure they are what you want before entering the information to initiate the block.

Technische Erklärung

CIDR notation is written as the IP address, a slash, and the CIDR suffix (for example, the IPv4 "" or IPv6 "a3:bc00::/24"). The CIDR suffix is the number of starting digits every IP address in the range have in common when written in binary.

For example: "" is binary "00001010.00001010.00000001.00100000", so will match the first 27 digits ("00001010.00001010.00000001.00100000"). The IP addresses, when converted to binary, all have the same 27 first digits and will be blocked if is blocked.

As the CIDR suffix increases, the block affects fewer IP addresses (see table of sample ranges). CIDR suffixes are not the same for IPv4 addresses as they are for IPv6 addresses; the same CIDR suffix in IPv4 blocks =79,228,162,514,264,337,593,543,950,336 times as many addresses in IPv6.

Calculating the CIDR suffix

You can use the table of sample ranges below to guess the range, use a computer script, or manually calculate the range.

Conversion to binary

The first step in manually calculating a range is to convert the first and last IP address to binary representation. (This assumes you're not using a computer script, which can probably calculate the range for you anyway.) An IP address is composed of four groups of eight ones and zeros. Each group represents a number from 0 to 255. To convert a number to binary, you can use a reference table or know the value of each binary digit:

Binary digit:   1   1   1   1   1   1   1   1
Value: 128  64  32  16   8   4   2   1

Proceeding from left to right, fill in 1 if the number is at least that value, and subtract that value (if it's not, fill in 0 and don't subtract). For example, to calculate 240:

  1. 240 is at least 128, so place 1 and subtract 128.
  2. 112 (240-128) is at least 64, so place 1 and subtract 64.
  3. 48 (112-64) is at least 32, so place 1 and subtract 32.
  4. 16 (48-32) is at least 16, so place 1 and subtract 16.
  5. Since the remaining value is zero, all the remaining places are 0.

Thus, 240 is 1111 0000 because it can be represented as 128+64+32+16+0+0+0+0.

Calculate range

  1. Place both IP addresses one atop the other, and count how many starting digits are exactly alike. This is the CIDR suffix.
  2. Double-check! Being off by one digit could extend your block by thousands of addresses.

The example below calculates the CIDR range between and Note that this is a simple example; some groups of IP addresses do not so neatly fit CIDR suffixes, and need multiple different-sized blocks to block the exact range.

IP addresses:
Convert to binary:
  0100 0101.1101 0000.0000 0000.0000 0000
  0100 0101.1101 0000.0000 0000.1111 1111
Count identical first numbers:
  0100 0101.1101 0000.0000 0000.0000 0000
  0100 0101.1101 0000.0000 0000.1111 1111
            24 digits
CIDR range:

Table of sample ranges

The table below shows the IPv4 blocks each CIDR suffix affects. Note that MediaWiki only supports blocking CIDR suffixes 16 - 32 in IPv4 and 19 (formerly 64) - 128 in IPv6 by default (subject to $wgBlockCIDRLimit ). See /IPv6 for an IPv6 range table.

CIDR Start Range End Range Total addresses Bits selected in IP address 4.294.967.296 ********.********.********.******** 2.147.483.648 0*******.********.********.******** 268.435.456 0100****.********.********.******** 16.777.216 01000101.********.********.******** 2.097.152 01000101.110*****.********.******** 1.048.576 01000101.1101****.********.******** 524.288 01000101.11010***.********.******** 262.144 01000101.110100**.********.******** 131.072 01000101.1101000*.********.******** 65.536 01000101.11010000.********.******** 32.768 01000101.11010000.0*******.******** 16.384 01000101.11010000.00******.******** 8.192 01000101.11010000.000*****.******** 4.096 01000101.11010000.0000****.******** 2.048 01000101.11010000.00000***.******** 1.024 01000101.11010000.000000**.******** 512 01000101.11010000.0000000*.******** 256 01000101.11010000.00000000.******** 128 01000101.11010000.00000000.0******* 64 01000101.11010000.00000000.00****** 32 01000101.11010000.00000000.000***** 16 01000101.11010000.00000000.0000**** 8 01000101.11010000.00000000.00000*** 4 01000101.11010000.00000000.000000** 2 01000101.11010000.00000000.0000000* 1 01000101.11010000.00000000.00000000

Default limitation

The default MediaWiki installation limits range blocks to no larger than /16 IPv4 rangeblocks (65,536 addresses). To block larger ranges $wgBlockCIDRLimit needs to be set accordingly in LocalSettings.php .


External links

  • Subnet Calculator can help calculate prefix length and subnet mask for IPv4 and IPv6.