IPv6 Address Visualizer
See how IPv6 global addresses are structured for aggregation — ISP /48 allocations, 65,536 /64 site subnets, SLA ID fields, and interface identifiers. Includes Modified EUI-64 and address-type reference.
Address input
Fully expanded, compressed, uppercase/lowercase, and /0–/128 prefixes.
IPv6 address. Expanded form: 2001:0db8:abcd:0012:021c:7eff:fe12:3456. Compressed form: 2001:db8:abcd:12:21c:7eff:fe12:3456, network prefix length 64.
ISP /48 allocation and aggregation layout
IPv6 was designed for route aggregation. A typical enterprise receives /48; you subnet the next 16 bits into /64 networks.
Typical enterprise allocation: /48 from the ISP
- An ISP often allocates a /48, leaving 16 bits (from /48 to /64) for your site subnets.
- That is 2^16 = 65,536 possible /64 subnets — each LAN, VLAN, or point-to-point link can use a full /64.
- There is no need to subnet smaller to save addresses. IPv6 is not conserved like IPv4; there is no NAT equivalent for global unicast.
- Think of a global IPv6 address like a public IPv4 address — abundant space means every interface can have a /64.
Compressed
2001:db8:abcd:12:21c:7eff:fe12:3456
Expanded
2001:0db8:abcd:0012:021c:7eff:fe12:3456
128-bit aggregation fields (RFC 2374 teaching model)
SLA ID (Site-Level Aggregation)
Your subnet field. From a /48, this 16-bit field yields 2^16 (65,536) /64 subnets.
- Bit range
- 48–63 (16 bits)
- Value (hex)
- 12
- CCNA / modern mapping
- Subnet ID (/48 → /64)
Your /48 site — modern CCNA breakdown
ISP-assigned site prefix
2001:db8:abcd:12/48
First 48 bits — summarize toward the provider.
Subnet field (SLA ID)
Decimal 18 · Hex 0x12
16 bits → 65,536 possible /64 subnets (216).
Interface identifier (/64)
21c:7eff:fe12:3456
Every subnet uses a full /64 — LAN, VLAN, or point-to-point. No need to subnet further to save addresses.
Cisco interface behavior
On Cisco routers, enabling IPv6 on an interface can assign multiple IPv6 addresses to that interface (global unicast, link-local, and others).
Why this layout exists
The original FP / TLA / NLA / SLA layout exists so providers can aggregate and summarize routes toward the internet core.
Detected type: documentation