Aiuto: Blocchi per intervalli di IP

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Fare riferimento a Help:Range blocks/IPv6 per ulteriori informazioni riguardo i blocchi IPv6.

I blocchi per intervalli sono restrizioni tecniche applicate attraverso Special:Block ad un gruppo di Indirizzi IP che li blocca dalla modifica di pagine, creazione di nuovi account, invio di email dall'interfaccia del wiki, etc. Se spunti la casella "Applica blocco agli utenti registrati da questo indirizzo IP" saranno disabilitate anche le modifiche degli utenti registrati se si connettono dal blocco degli indirizzi bloccati.

To block an IP range from Special:Block, enter the first IP address in the range followed by a forward slash and a Classless inter-domain routing (CIDR) suffix.

You should avoid performing range blocks unless you understand what you are doing, or you may end up blocking tens of thousands or even millions of people who are not the problem!

This article mainly discusses IPv4; IPv6 blocks work similarly, but have different implications—see /IPv6.

Spiegazione non tecnica

Gli indirizzi IP sono suddivisi in blocchi di numeri. Un esempio sarebbe da 148.20.57.0 a 148.20.57.255. Una volta raggiunto il 255, l'indirizzo successivo è 148.20.58.0.

Gli indirizzi IP possono essere suddivisi in blocchi di varie dimensioni. Il blocco pratico più piccolo è quello da 4. Che potrebbe essere, per esempio, uno dei seguenti:

148.20.57.0 - 148.20.57.3,

148.20.57.4 - 148.20.57.7,

148.20.57.8 - 148.20.57.11, ...

Di ogni blocco da 4 indirizzi solo due di questi possono essere assegnati ad un computer. Il primo e l'ultimo numero di ogni blocco sono riservati alla comunicazione di rete. Questi sono blocchi di livello 30 e possono essere così espressi:

148.20.57.0/30,

148.20.57.4/30,

148.20.57.8/30, ...

Il blocco più largo successivo è di 8. Essi possono rappresentarsi come segue:

148.20.57.0 - 148.20.57.7,

148.20.57.8 - 148.20.57.15,

148.20.57.16 - 148.20.57.23, ...

Di questi 8 indirizzi, solo 6 possono essere assegnati ad un computer dato che, come precedentemente menzionato, il primo e l'ultimo indirizzo di ogni blocco sono riservati ad usi specifici nelle comunicazioni di rete. Questi possono anche essere espressi come segue:

148.20.57.0/29,

148.20.57.8/29,

148.20.57.16/29, ...

Da questo punto in poi, il numero di indirizzi IP in ogni blocco continua a raddoppiare: 16, 32, 64, 128, 256, etc.

Un blocco da 16 si esprimerebbe con 148.20.57.0/28.

Un blocco da 32 si esprimerebbe con 148.20.57.0/27.

Un blocco da 64 si esprimerebbe con 148.20.57.0/26.

Un blocco da 128 si esprimerebbe con 148.20.57.0/25.

Un blocco da 256 si esprimerebbe con 148.20.57.0/24.

Quindi, se hai un indirizzo IP di cui vuoi bloccare il blocco di appartenenza, come fai a sapere quale utilizzare? Immaginiamo tu abbia qualche problema con 148.20.57.34. Puoi individuare chi possiede questo indirizzo IP visitando 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. Blocca una gamma solo se c'è una serie di indirizzi IP che sta dando problemi.

C'è un calcolatore che è molto utile per questo:

toolforge:ftools/general/ip-range-calc.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.

Spiegazione tecnica

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 10.10.1.32–10.10.1.63, 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 $2^{96}$ =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:

240 is at least 128, so place 1 and subtract 128.
112 (240-128) is at least 64, so place 1 and subtract 64.
48 (112-64) is at least 32, so place 1 and subtract 32.
16 (48-32) is at least 16, so place 1 and subtract 16.
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

Place both IP addresses one atop the other, and count how many starting digits are exactly alike. This is the CIDR suffix.
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.

Example IP4 ranges
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 .

Known problems

One important already-known problem caused by any range-block, is that as side-effect they also block some trusted registered groups, like wiki administrators, users who do not need to be patrolled by others, and trusted bots. Details: phabricator:T309328

References

Classless Inter-Domain Routing

External links

Netmask calculator which helps in making the correct decision for range blocks.

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

toolforge:ftools/general/ip-range-calc.html gives you the range you should use when blocking.

IPv4 and CIDR Calculator gives you a breakdown of Hosts and IP Range for any Given Mask/CIDR and reverse.