{"licence":{"name":"CC BY-SA 4.0","spdx":"CC-BY-SA-4.0","url":"https://creativecommons.org/licenses/by-sa/4.0/","attribution":"Atlas, a bilingual technical dictionary (https://cmaintz.github.io/tech-atlas/)"},"id":"cs/ip-address","url":{"en":"https://cmaintz.github.io/tech-atlas/en/terms/cs/ip-address/","da":"https://cmaintz.github.io/tech-atlas/da/terms/cs/ip-address/"},"term":{"en":"IP address","da":"IP-adresse"},"aka":{"en":["Internet Protocol address","IPv4 address","IPv6 address"],"da":["IPv4-adresse","IPv6-adresse"]},"domain":["cs"],"cluster":"networking","layer":"network","status":"current","era":1981,"summary":{"en":"A number that identifies a device on a network so that data can be delivered to it.","da":"Et nummer, der identificerer en enhed på et netværk, så data kan leveres til den."},"body":{"formal":{"en":"A numeric label assigned to a device's network connection, which the TCP/IP protocols use to mark where each packet comes from and where it must go. IPv4 addresses are 32 bits long; IPv6 addresses are 128 bits.","da":"En talværdi, der tildeles en enheds netværksforbindelse, og som TCP/IP-protokollerne bruger til at angive, hvor hver pakke kommer fra, og hvor den skal hen. IPv4-adresser er på 32 bit, IPv6-adresser på 128 bit."},"plain":{"en":"Like a street address for a house - without it, the postman has no idea where to deliver the letter.","da":"Som en gadeadresse til et hus - uden den aner postbudet ikke, hvor brevet skal afleveres."},"inPractice":{"en":"An analyst in a region's SOC sees hundreds of failed logins to the hospitals' remote access, all from one IP address abroad, and blocks that address in the firewall.","da":"En analytiker i regionens SOC ser hundredvis af mislykkede login til hospitalernes fjernadgang, alle fra én IP-adresse i udlandet, og blokerer adressen i firewallen."},"whyItMatters":{"en":"Blocking, logging and tracing attacks all start from addresses, yet an address alone does not prove who is behind it - many users can share one, and attackers often borrow someone else's.","da":"Når man blokerer, logger og sporer angreb, tager man udgangspunkt i adresser, men en adresse alene beviser ikke, hvem der står bag - mange brugere kan dele én, og angribere låner ofte andres."}},"deepDive":{"en":"An IPv4 address (RFC 791, 1981) is 32 bits, written as four decimal octets such as 192.0.2.10. Every address is split into a network prefix and a host part. The original classful scheme (classes A, B and C) wasted space and was replaced in 1993 by Classless Inter-Domain Routing (CIDR, now RFC 4632), where the prefix length is written explicitly: 192.0.2.0/24 covers 256 addresses, and routers forward by longest prefix match. Several blocks are reserved: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 for private networks (RFC 1918), 127.0.0.0/8 for loopback, 169.254.0.0/16 for link-local autoconfiguration, 100.64.0.0/10 for carrier-grade NAT (RFC 6598) and 192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24 for documentation (RFC 5737).\n\nWith only about 4.3 billion possible addresses, IPv4 ran out: IANA allocated its last free blocks to the regional registries in February 2011, and RIPE NCC made its final IPv4 allocations in November 2019. Network address and port translation (NAT/NAPT) keeps IPv4 working by letting many devices share one public address, with the router rewriting source ports. That is also why an address plus a timestamp often cannot identify a subscriber behind carrier-grade NAT unless the source port was logged as well.\n\nIPv6 (RFC 8200) uses 128-bit addresses written as eight groups of hexadecimal digits, with runs of zeros compressed as :: (canonical form in RFC 5952), for example 2001:db8::1 from the documentation prefix 2001:db8::/32. A subnet is normally a /64, and hosts often configure themselves via SLAAC (RFC 4862), typically with temporary privacy addresses that change over time (RFC 8981). Every IPv6 interface also has a link-local fe80::/10 address and usually several global ones. A common blind spot is that operating systems enable IPv6 by default, so networks that filter and monitor only IPv4 may have unmanaged IPv6 paths, and rogue router advertisements can redirect traffic unless mitigated with RA Guard (RFC 6105).\n\nAddresses are assigned statically, by DHCP (RFC 2131) or DHCPv6, and mapped to link-layer MAC addresses by ARP (RFC 826) in IPv4 and Neighbor Discovery in IPv6. As evidence of identity an address is weak: source addresses can be spoofed in one-way traffic such as UDP floods, although a completed TCP handshake shows that the sender could at least receive packets sent to that address. Attackers routinely use VPNs, cloud hosts and residential proxy networks, so blocklisting single addresses has limited effect, and geolocation databases are approximate. Legally, the Court of Justice of the EU held in Breyer (C-582/14, 2016) that a dynamic IP address can be personal data for a website operator that has legal means to identify the user, so IP logs fall under the GDPR.","da":"En IPv4-adresse (RFC 791, 1981) er på 32 bit og skrives som fire decimale oktetter, fx 192.0.2.10. Hver adresse deles i et netværkspræfiks og en værtsdel. Det oprindelige klassebaserede system (klasse A, B og C) spildte adresser og blev i 1993 afløst af Classless Inter-Domain Routing (CIDR, nu RFC 4632), hvor præfiksets længde angives eksplicit: 192.0.2.0/24 dækker 256 adresser, og routere videresender efter længste præfiksmatch. En række blokke er reserveret: 10.0.0.0/8, 172.16.0.0/12 og 192.168.0.0/16 til private netværk (RFC 1918), 127.0.0.0/8 til loopback, 169.254.0.0/16 til link-local-autokonfiguration, 100.64.0.0/10 til carrier-grade NAT (RFC 6598) og 192.0.2.0/24, 198.51.100.0/24 og 203.0.113.0/24 til dokumentation (RFC 5737).\n\nMed kun omkring 4,3 milliarder mulige adresser løb IPv4 tør: IANA tildelte sine sidste frie blokke til de regionale registre i februar 2011, og RIPE NCC foretog sine sidste IPv4-tildelinger i november 2019. Adresse- og portoversættelse (NAT/NAPT) holder IPv4 kørende ved at lade mange enheder dele én offentlig adresse, hvor routeren omskriver kildeportene. Det er også grunden til, at en adresse og et tidsstempel ofte ikke kan identificere en kunde bag carrier-grade NAT, medmindre kildeporten også er logget.\n\nIPv6 (RFC 8200) bruger 128-bit adresser skrevet som otte grupper hexadecimale cifre, hvor sekvenser af nuller forkortes med :: (kanonisk form i RFC 5952), fx 2001:db8::1 fra dokumentationspræfikset 2001:db8::/32. Et subnet er normalt et /64, og værter konfigurerer sig ofte selv via SLAAC (RFC 4862), typisk med midlertidige privatlivsadresser, der skifter over tid (RFC 8981). Hver IPv6-grænseflade har desuden en link-local-adresse i fe80::/10 og som regel flere globale adresser. Et almindeligt blindt punkt er, at styresystemer har IPv6 slået til som standard, så netværk, der kun filtrerer og overvåger IPv4, kan have ustyrede IPv6-veje, og falske router advertisements kan omdirigere trafik, medmindre man bruger RA Guard (RFC 6105).\n\nAdresser tildeles statisk, via DHCP (RFC 2131) eller DHCPv6 og kobles til linklagets MAC-adresser med ARP (RFC 826) i IPv4 og Neighbor Discovery i IPv6. Som bevis for identitet er en adresse svag: Afsenderadresser kan forfalskes i envejstrafik som UDP-oversvømmelser, men et gennemført TCP-håndtryk viser dog, at afsenderen kunne modtage pakker sendt til adressen. Angribere bruger rutinemæssigt VPN, cloud-servere og netværk af residential proxies, så blokering af enkelte adresser har begrænset effekt, og geolokationsdatabaser er omtrentlige. Juridisk fastslog EU-Domstolen i Breyer-sagen (C-582/14, 2016), at en dynamisk IP-adresse kan være en personoplysning for en webstedsoperatør, der har lovlige midler til at identificere brugeren, så IP-logs er omfattet af databeskyttelsesforordningen."},"edges":[{"type":"requires","to":"cs/network","confidence":"high","strength":"normal"},{"type":"used-with","to":"cs/port","confidence":"high","strength":"normal"}],"depth":1,"sources":[{"title":"Kurose & Ross, Computer Networking: A Top-Down Approach","tier":"textbook"},{"title":"RFC 791 - Internet Protocol","tier":"standard"}],"draft":true}