128-Bit Next-Generation Networking
IPv6 Subnet Calculator
Full 128-bit precision IPv6 calculator. Expand compressed addresses, calculate prefix boundaries, total /64 subnets, and generate ip6.arpa reverse DNS.
Accepts compressed or full notation
Routing prefix size
Network Prefix
2001:db8:85a3::/64
Subnet routing identifier
Total /64 Subnets
1
2^(64 - prefix) subnets
Address Scope
Documentation
IANA / RFC classification
Total Host Space
18.4 Quintillion IPs
2^(128 - prefix)
RFC 5952 Compressed Format:
2001:db8:85a3::8a2e:370:7334
Full Expanded 32-Hex Format:
2001:0db8:85a3:0000:0000:8a2e:0370:7334
Reverse DNS (ip6.arpa):
4.3.3.7.0.7.3.0.e.2.a.8.0.0.0.0.0.0.0.0.3.a.5.8.8.b.d.0.1.0.0.2.ip6.arpa
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Frequently Asked Questions
Clear answers to common questions about subnetting, CIDR notation, and network design.
How many IP addresses are in a standard /64 IPv6 subnet?
A standard IPv6
/64 subnet contains 2^64 addresses, which is approximately 18,446,744,073,709,551,616 (18.4 quintillion) individual IP addresses. In IPv6, unlike IPv4, there are no broadcast addresses, and /64 is the universal standard prefix size required for SLAAC (Stateless Address Autoconfiguration).What is the difference between Compressed and Expanded IPv6?
Expanded IPv6 displays all 8 hextets with 4 hexadecimal characters each (e.g.
2001:0db8:0000:0000:0000:0000:0000:0001). Compressed IPv6 follows RFC 5952: leading zeros inside a hextet are stripped, and the longest contiguous block of all-zero hextets is replaced with a double colon :: (e.g. 2001:db8::1).What are common IPv6 prefix allocations?
Typical IPv6 allocations from Regional Internet Registries (RIRs) and ISPs include: /32 to ISPs and telecom carriers; /48 to large enterprise businesses; /56 to residential and small business customers; and /64 as the standard single end-user subnet for devices.