ADDRESS PLANNING / REAL CALCULATIONS
Subnet & CIDR calculator
Find the network boundary, address range and size of an IPv4 or IPv6 prefix. Calculations stay on this server; no traffic is sent to the address.
Your network, decoded.
- Network prefix
- 2001:db8::/64
- IP version
- 6
- Netmask
- ffff:ffff:ffff:ffff::
- Broadcast address (IPv4)
- Not applicable
- First address in range
- 2001:db8::
- Last address in range
- 2001:db8::ffff:ffff:ffff:ffff
- Total addresses
- 18446744073709551616
- Addresses in range
- 18446744073709551616
IPv6 has no broadcast. This range includes every address in the prefix; reserved and interface-specific uses still need planning.
Your host address was normalised to its network prefix.
Choose the right diagnostic tool
These commands are references for your own terminal. This website does not execute them or contact a target.
- Wireshark — inspect packets captured on an authorised interface.
- tcpdump — capture traffic with a small, explicit filter.
- Nmap — discover hosts and services only on networks you are authorised to assess.
- iperf3 — compare throughput between endpoints you control.
Read the result in context
A tool gives you an observation, not a diagnosis. Check the transport, endpoint and assumptions before drawing a conclusion.
- A timeout may be caused by filtering, rate limiting or a return-path issue.
- A listening port says little about application correctness.
- A public DNS answer can differ from an internal answer.
- Keep outputs free of credentials and personal information when sharing them.