everydayapps.io / networkcalc
IPv6 Quick Reference
Notation rules, address types, prefix conventions, and multicast. Two-sided print — notation & types on page 1, prefixes & multicast on page 2.
Notation rules
- 128 bits, written as 8 groups of 4 hex digits joined by colons.
- Leading zeros in any group MAY be dropped — 0db8 becomes db8.
- One run of consecutive all-zero groups MAY be collapsed to "::".
- Only one "::" per address — the reader must be able to recover all 8 groups.
- Prefix length is "/N" just like IPv4 CIDR (e.g. 2001:db8::/32).
Abbreviation examples
| Expanded | Shortened |
|---|---|
| 2001:0db8:0000:0000:0000:0000:0000:0001 | 2001:db8::1 |
| fe80:0000:0000:0000:0202:b3ff:fe1e:8329 | fe80::202:b3ff:fe1e:8329 |
| ff02:0000:0000:0000:0000:0000:0000:0001 | ff02::1 |
| 0000:0000:0000:0000:0000:0000:0000:0000 | :: |
Address types & well-known blocks
| Block | Name | Usage |
|---|---|---|
| 2000::/3 | Global Unicast (GUA) | Globally routable unicast. |
| fc00::/7 | Unique Local (ULA) | Enterprise-internal — not globally routed. |
| fe80::/10 | Link-local | Auto-assigned per interface; link-scope only. |
| ff00::/8 | Multicast | One-to-many delivery, per-scope. |
| ::1/128 | Loopback | Host itself (IPv6 localhost). |
| ::/128 | Unspecified | Source placeholder before config. |
| ::ffff:0:0/96 | IPv4-mapped | Dual-stack socket representation of an IPv4 peer. |
| 2001:db8::/32 | Documentation | Examples only — never route. |
Address structure (global unicast)
Global routing prefix 48 bits
Subnet ID 16 bits
Interface identifier 64 bits
A /48 from your ISP gives you 216 (65,536) /64 LAN prefixes. Each LAN's host portion (the 64-bit interface ID) accommodates SLAAC or DHCPv6 assignment.
Prefix conventions
| Prefix | Typical use | Notes |
|---|---|---|
| /32 | ISP allocation | Typical RIR allocation to a large ISP. |
| /48 | Site | Typical site (enterprise, school, small ISP handoff). |
| /56 | Small site | Residential / branch office split. |
| /64 | LAN | Single subnet — required for SLAAC. |
| /126 | Router p2p | Legacy p2p usage (4 addresses). |
| /127 | Point-to-point | Modern p2p link per RFC 6164. |
| /128 | Single host | Host route / loopback / special addresses. |
Multicast scope prefixes
| Prefix | Scope | Notes |
|---|---|---|
| ff01 | Interface-local | Same interface only. |
| ff02 | Link-local | Same link — most common. |
| ff04 | Admin-local | Administrator-defined. |
| ff05 | Site-local | Single site. |
| ff08 | Org-local | Organization-wide. |
| ff0e | Global | Internet-wide. |
Well-known multicast
| ff02::1 | All nodes on link |
|---|---|
| ff02::2 | All routers on link |
| ff02::5 | OSPFv3 All Routers |
| ff02::6 | OSPFv3 DR |
| ff02::9 | RIPng routers |
| ff02::a | EIGRP routers |
| ff02::d | PIM routers |
| ff02::12 | VRRP |
| ff02::16 | MLDv2 reports |
| ff02::1:2 | All DHCPv6 agents |
| ff02::fb | mDNS (IPv6) |
| ff02::1:ff00:0/104 | Solicited-node range |
Solicited-node multicast formula
ff02::1:ff + last 24 bits of target address
Target
2001:db8::abcd:1234 → SN ff02::1:ffcd:1234Target
fe80::1:2:3:4 → SN ff02::1:ff02:304