Kernaali ToolsRead the address
2001:db8:4a10:0023:0000:0000:0000:009a/64
128 bits = eight 16-bit hexadecimal groups. Here the first four groups identify the /64 prefix; the remaining four are the interface-ID portion.
Canonical form: 2001:db8:4a10:23::9a/64. Drop leading zeros within groups. Replace the longest run of two or more zero groups with :: once; use the leftmost run on a tie. Never drop trailing zeros from a group.
| Prefix / address | Meaning | Operational detail |
|---|---|---|
| ::/128 | Unspecified | Used before an address is available; not a destination |
| ::1/128 | Loopback | Local host only |
| fe80::/10 | Link-local | Routers do not forward it to other links |
| fc00::/7 | Unique local | Locally generated prefixes use fd00::/8 + random 40-bit global ID |
| 2001:db8::/32 | Documentation | Use for published examples |
| ff00::/8 | Multicast | Scope is encoded in the address |
| ff02::1 | All nodes on link | Link-scoped multicast |
| ff02::2 | All routers on link | Link-scoped multicast |
| ff02::1:ff00:0/104 | Solicited-node multicast | Last 24 bits come from the unicast/anycast address |
Prefixes in a plan
| Prefix | Common use / arithmetic |
|---|---|
| /48 | 65,536 separate /64s |
| /56 | 256 separate /64s |
| /60 | 16 separate /64s |
| /64 | Usual SLAAC LAN prefix |
| /127 | Router point-to-point link (RFC 6164) |
| /128 | Single host route |
A /64 is the normal LAN/SLAAC design, not a rule that every route must be /64. There is no IPv6 broadcast and no general “subtract two hosts” rule.
Reverse DNS and scope
Reverse the 32 hexadecimal digits and append ip6.arpa.; each digit is a DNS label. A /48 reverse zone uses 12 prefix nibbles, in reverse order. Delegate on a 4-bit boundary.
For 2001:db8:4a10::/48, the reverse zone is 0.1.a.4.8.b.d.0.1.0.0.2.ip6.arpa.
A link-local address may need an interface scope such as %eth0 in a host tool. The zone suffix is local context, not part of the 128-bit address.
Before enabling IPv6: allow required ICMPv6 (including Neighbor Discovery and Packet Too Big), deploy explicit firewall policy, and test DNS AAAA reachability.