Help:Rangeblokkades

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This page is a translated version of the page Help:Range blocks and the translation is 20% complete.
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Lees /IPv6 voor meer informatie over IPv6-rangeblokkades.

Rangeblokkades zijn technische restricties opgelegd via Special:Block aan een groep van IP-adressen dat voorkomt dat daarmee kan worden bewerkt, nieuwe accounts kunnen worden aangemaakt, e-mails kunnen worden verzonden via de wiki-interface etc. Als je "Deze blokkade ook toepassen op aangemelde gebruikers die van dit IP-adres gebruik maken" aanvinkt, worden ook bewerkingen van geregistreerde gebruikers geblokkeerd als deze zijn gedaan vanaf een geblokkeerde range.

Om een IP-range te blokkeren via Special:Block, voer je het eerste IP-adres van de range in, gevolgd door een schuine streep en een 'Classless inter-domain routing' (CIDR) suffix. Je moet rangeblokkades zoveel mogelijk vermijden tenzij je begrijpt wat je doet, anders loop je het risico dat je tienduizenden of zelfs miljoenen mensen blokkeert die geen onderdeel van het probleem zijn.

Dit artikel bespreekt voornamelijk IPv4; IPv6-blokkades werken op dezelfde manier, maar hebben verschillende implicaties - zie ook /IPv6.

Niet-technische uitleg

IP-adressen zijn opgedeeld in blokken van nummers. Een voorbeeld hiervan zou zijn 148.20.57.0 door naar 148.20.57.255. Als het 255 bereikt, is het volgende nummer 148.20.58.0.

IP-adressen kunnen worden opgedeeld in kleinere of grotere blokken. Het kleinste praktische blok is een blok van 4. Dit kan een van de volgende zijn:

148.20.57.0 - 148.20.57.3,
148.20.57.4 - 148.20.57.7,
148.20.57.8 - 148.20.57.11, ...

Van elk blok van 4 nummers, kunnen er maar twee worden toegewezen aan een computer. De eerste en laatste nummers van elk blok worden gereserveerd voor netwerkcommunicatie. Deze zijn level 30-blokken en kunnen als volgt worden uitgedrukt:

148.20.57.0/30,
148.20.57.4/30,
148.20.57.8/30, ...

Het op een na grootste blok is 8. Ze kunnen als volgt zijn:

148.20.57.0 - 148.20.57.7,
148.20.57.8 - 148.20.57.15,
148.20.57.16 - 148.20.57.23, ...

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:

148.20.57.0/29,
148.20.57.8/29,
148.20.57.16/29, ...

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 148.20.57.0/28.
A block of 32 would start 148.20.57.0/27.
A block of 64 would start 148.20.57.0/26.
A block of 128 would start 148.20.57.0/25.
A block of 256 would start 148.20.57.0/24.

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 148.20.57.34. You can lookup who has this IP address at http://arin.net/whois/?queryinput=148.20.57.34. 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:

http://www.csgnetwork.com/ipinfocalc.html

Go to this site and enter 148.20.57.34 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 148.20.57.34. (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.

Technical explanation

CIDR notation is written as the IP address, a slash, and the CIDR suffix (for example, the IPv4 "10.2.3.41/24" 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: "10.10.1.32" is binary "00001010.00001010.00000001.00100000", so 10.10.1.32/27 will match the first 27 digits ("00001010.00001010.00000001.00100000"). The IP addresses 10.10.1.3210.10.1.63, when converted to binary, all have the same 27 first digits and will be blocked if 10.10.1.32/27 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 69.208.0.0 and 69.208.0.255. 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:
  69.208.0.0
  69.208.0.255
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:
  69.208.0.0/24

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
69.208.0.0/0 0.0.0.0 255.255.255.255 4.294.967.296 ********.********.********.********
69.208.0.0/1 0.0.0.0 127.255.255.255 2.147.483.648 0*******.********.********.********
69.208.0.0/4 64.0.0.0 79.255.255.255 268.435.456 0100****.********.********.********
69.208.0.0/8 69.0.0.0 69.255.255.255 16.777.216 01000101.********.********.********
69.208.0.0/11 69.192.0.0 69.223.255.255 2.097.152 01000101.110*****.********.********
69.208.0.0/12 69.208.0.0 69.223.255.255 1.048.576 01000101.1101****.********.********
69.208.0.0/13 69.208.0.0 69.215.255.255 524.288 01000101.11010***.********.********
69.208.0.0/14 69.208.0.0 69.211.255.255 262.144 01000101.110100**.********.********
69.208.0.0/15 69.208.0.0 69.209.255.255 131.072 01000101.1101000*.********.********
69.208.0.0/16 69.208.0.0 69.208.255.255 65.536 01000101.11010000.********.********
69.208.0.0/17 69.208.0.0 69.208.127.255 32.768 01000101.11010000.0*******.********
69.208.0.0/18 69.208.0.0 69.208.63.255 16.384 01000101.11010000.00******.********
69.208.0.0/19 69.208.0.0 69.208.31.255 8.192 01000101.11010000.000*****.********
69.208.0.0/20 69.208.0.0 69.208.15.255 4.096 01000101.11010000.0000****.********
69.208.0.0/21 69.208.0.0 69.208.7.255 2.048 01000101.11010000.00000***.********
69.208.0.0/22 69.208.0.0 69.208.3.255 1.024 01000101.11010000.000000**.********
69.208.0.0/23 69.208.0.0 69.208.1.255 512 01000101.11010000.0000000*.********
69.208.0.0/24 69.208.0.0 69.208.0.255 256 01000101.11010000.00000000.********
69.208.0.0/25 69.208.0.0 69.208.0.127 128 01000101.11010000.00000000.0*******
69.208.0.0/26 69.208.0.0 69.208.0.63 64 01000101.11010000.00000000.00******
69.208.0.0/27 69.208.0.0 69.208.0.31 32 01000101.11010000.00000000.000*****
69.208.0.0/28 69.208.0.0 69.208.0.15 16 01000101.11010000.00000000.0000****
69.208.0.0/29 69.208.0.0 69.208.0.7 8 01000101.11010000.00000000.00000***
69.208.0.0/30 69.208.0.0 69.208.0.3 4 01000101.11010000.00000000.000000**
69.208.0.0/31 69.208.0.0 69.208.0.1 2 01000101.11010000.00000000.0000000*
69.208.0.0/32 69.208.0.0 69.208.0.0 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 .

References

External links

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