Suggest an editImprove this articleRefine the answer for “What is IPv6?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**IPv6 (Internet Protocol version 6)** is a new version of the internet protocol, designed as a replacement for IPv4. **Key point:** IPv6 uses 128-bit addressing (versus 32-bit in IPv4), does not require NAT, and does not use broadcast.Shown above the full answer for quick recall.Answer (EN)Image**IPv6 (Internet Protocol version 6)** is a new version of the internet protocol, designed as a replacement for IPv4. Its main goal is to provide **a huge number of IP addresses** and remove the limitations of the old version. Short wording for an interview: > **IPv6 is a 128-bit network protocol that provides addressing and routing for devices on the internet. It replaced IPv4 due to a shortage of addresses and added a simpler header, built-in security, and automatic configuration.** --- ## The main difference: address space size IPv4 → **32 bits** (≈ 4.3 billion addresses) IPv6 → **128 bits** (≈ 3.4 × 10³⁸ addresses) This means: - enough addresses for every device on the planet - NAT is no longer required - every device can be given a *globally unique address* --- ## The structure of an IPv6 address An IPv6 address is **128 bits**, written as 8 groups of 4 hexadecimal digits: Example: ``` 2001:0db8:85a3:0000:0000:8a2e:0370:7334 ``` It can be shortened: 1. Remove leading zeros: ``` 2001:db8:85a3:0:0:8a2e:370:7334 ``` 2. Replace consecutive zero groups with :: ``` 2001:db8:85a3::8a2e:370:7334 ``` **The :: shorthand can be used only once**. --- ## Types of IPv6 addresses ### **1. Global Unicast (global addresses)** The equivalent of public IPv4 addresses. Routed on the internet. Usually start with **2000::/3**. ### **2. Link-local** For communication within a single link (one L2 network). Automatically assigned to all interfaces: ``` fe80::/10 ``` The equivalent of IPv4 APIPA (169.254.x.x), but mandatory and always in use. ### **3. Unique Local Address (ULA)** Private, local addresses in IPv6 (the equivalent of RFC1918 in IPv4): ``` fc00::/7 ``` ### **4. Multicast** A replacement for broadcast (which does not exist in IPv6): ``` ff00::/8 ``` --- ## IPv6 does not use broadcast **Multicast** is used instead, which: - reduces load, - makes the network more efficient. --- ## Main advantages of IPv6 #### **1. A huge number of addresses** Every device: a unique global IP. #### **2. A simplified header** The IPv6 header is simpler and processed faster by routers. #### **3. SLAAC: automatic configuration** A device can obtain a global IPv6 address on its own, without DHCP. #### **4. No NAT** Every host can be directly reachable (unless blocked by a firewall). #### **5. Built-in IPSec support** Security at the network layer. #### **6. Improved routing and multicast** --- ## The structure of an IPv6 packet The IPv6 header is simpler than in IPv4: Main fields: - Version - Traffic Class - Flow Label - Payload Length - Next Header - Hop Limit - Source Address - Destination Address There is no: - checksum - fragmentation by routers (only by the host) This speeds up processing. --- ## Comparison of IPv4 and IPv6 | Parameter | IPv4 | IPv6 | |---|---|---| | Address size | 32 bits | 128 bits | | Addresses | ~4.3 billion | ≈3.4 × 10³⁸ | | Notation | 192.168.1.1 | 2001:db8::1 | | Broadcast | Yes | No | | NAT | Often required | Not required | | Auto-configuration | DHCP | SLAAC + DHCPv6 | | Security | External mechanisms | IPSec built in | --- ## Example of IPv6 addresses in a real network Link-local address (present on all interfaces): ``` fe80::1c2e:4ff:feab:1234 ``` Global address: ``` 2001:67c:240:abcd::15 ``` ULA (local address): ``` fd00:1234:abcd::1 ``` --- ## Ready answer for an interview > **IPv6 is a 128-bit network-layer protocol created to replace IPv4 due to a shortage of addresses.** > **It uses hexadecimal notation, supports SLAAC, does not use broadcast, has built-in IPSec, and provides a huge address space.** > **IPv6 addresses are divided into global unicast, link-local, ULA, and multicast.** --- ## Cheat sheet (5 seconds) - IPv6 = 128 bits, hexadecimal addresses. - Does not use broadcast → multicast. - Addresses: global, link-local (fe80::), ULA (fc00::), multicast (ff00::). - Supports SLAAC and built-in IPSec. - Solves the problem of IPv4 shortage.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.