user@netcalc ~/calc $
ipv4_calculator
Calculate network, broadcast, mask, hosts, class and binary for any IPv4 address
ip:
mask:
✓ stdout — ipv4_calculator
Enter runs the calculation · Shift+Enter inserts a new line
user@netcalc ~/calc $
ipv6_calculator
Calculate network info for IPv6 addresses in CIDR notation
ipv6:
pfx:
✓ stdout — ipv6_calculator
user@netcalc ~/calc $
vlsm_calculator
Variable Length Subnet Mask — assigns optimal blocks for each network segment
net:
pfx:
// Subnets required
name:
hosts:
name:
hosts:
name:
hosts:
✓ stdout — vlsm_calculator
| # | Name | Hosts Req | Hosts Avail | Prefix | Network | First Host | Last Host | Broadcast | Mask |
|---|
user@netcalc ~/calc $
usable_ip_range
Shows the exact usable host range for a given network
ip:
mask:
✓ stdout — usable_ip_range
user@netcalc ~/calc $
binary_ip_calc
Convert IP addresses to binary and vice versa, with per-octet visualization
dec:
bin:
✓ stdout — binary_ip_calc
user@netcalc ~/network $
cidr_converter
Convert between CIDR, decimal mask and wildcard. Includes full /1–/32 reference table.
in:
✓ stdout — cidr_converter
📋 CIDR Reference Table
| CIDR | Subnet Mask | Wildcard | Hosts | /24 subnets | Block |
|---|
user@netcalc ~/network $
wildcard_mask_calc
Calculate the wildcard (inverse) mask for Cisco ACLs, OSPF and firewall rules
mask:
✓ stdout — wildcard_mask_calc
user@netcalc ~/network $
supernet_calculator
Find the minimum supernet containing all specified networks (route summarization)
nets:
✓ stdout — supernet_calculator
user@netcalc ~/network $
subnet_splitter
Split a network into equal subnets by specifying a new prefix
net:
mask:
new:
✓ stdout — subnet_splitter
| # | Network | First Host | Last Host | Broadcast | Hosts | Mask |
|---|
user@netcalc ~/network $
range_to_cidr
Convert an IP range (start–end) to the minimum set of CIDR blocks
start:
end:
✓ stdout — range_to_cidr
| # | CIDR Block | Network | Broadcast | Hosts |
|---|
user@netcalc ~/network $
ip_to_integer
Convert IPv4/IPv6 addresses to integer and vice versa
ip:
int:
✓ stdout — ip_to_integer
user@netcalc ~/network $
ipv6_normalize
Expand and compress IPv6 addresses — normalize any valid format
ipv6:
✓ stdout — ipv6_normalize
user@netcalc ~/network $
hex_ip_converter
Convert between hexadecimal and IP address — useful for Windows route tables and Cisco logs
ip:
0x:
✓ stdout — hex_ip_converter
user@netcalc ~/network $
vlan_calculator
802.1Q VLAN info: tag encoding, PCP, DEI, VID, range and compatibility
vlan:
pcp:
dei:
✓ stdout — vlan_calculator
user@netcalc ~/dns $
reverse_dns_generator
Generate the PTR in-addr.arpa zone for an IPv4 network
net:
pfx:
dom:
✓ stdout — reverse_dns_generator
user@netcalc ~/dns $
ipv6_ptr_generator
Generate the PTR ip6.arpa record for an IPv6 address
ipv6:
host:
✓ stdout — ipv6_ptr_generator
user@netcalc ~/dns $
ip_geolocation
Locate a public IP or resolve a domain and geolocate its public address
Domains are resolved through DNS first; geolocation is based on the resulting public IP.
geo:
✓ stdout — ip_geolocation
user@netcalc ~/dns $
ip_address_planner
Interactive IP address space planner — click cells to edit, export to CSV
📋 IP Address Plan
| # | Name | Network | Mask/CIDR | Gateway | VLAN | Location | Notes |
|---|
user@netcalc ~/legal $
Privacy
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Calculations are sent through this site's same-origin Worker proxy to the private calculation service.
Performance metrics
LCP, CLS and INP may be stored as aggregate performance measurements by tool and language. Calculation inputs and persistent user identifiers are not included.
GeoIP
Only GeoIP lookups are processed by an external provider. The requested IP address is sent for that lookup.
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This page provides operational information; it is not a legal-compliance certification.
RDAP vs ASN vs GeoIP: what each lookup actually tells you
Separate registration, routing ownership, DNS and approximate location so network investigations use the right evidence.
01
RDAP answers registration questions
RDAP is about registered resources: an IP network, autonomous system or domain, its handle, status, events and associated entities. It is authoritative for allocation context when you query the correct registry.
02
ASN data answers routing-ownership questions
An ASN lookup helps identify the network that originates or is associated with a public address. That is useful for routing context, but the ASN is not the same thing as the website owner or the physical location of a user.
03
GeoIP is an estimate
Geolocation providers infer country, region or city from routing and commercial datasets. The result can be useful for broad context while being wrong at city level, especially with mobile networks, VPNs, CDNs and anycast.
04
DNS provides another independent layer
A domain name can resolve to infrastructure operated by a CDN or hosting provider. Combining DNS, ASN and RDAP gives stronger context than treating any one lookup as a complete identity source.
05
Build a chain of evidence instead of one “owner” field
A useful investigation records what each source actually claims. DNS says where a name resolves, ASN data says who originates a route, RDAP says how an Internet resource is registered and GeoIP estimates location. These facts can point to different organizations without contradicting each other.
06
Expect CDN, anycast and cloud abstraction
A single hostname may return different addresses by region, while one anycast address is announced from many physical sites. Cloud customers can also use provider-owned prefixes. This is why ASN or RDAP ownership should not be presented as proof of website ownership or user location.
07
Record time and source when results matter
Routing, DNS and registration data change. For troubleshooting or incident notes, record the query, timestamp and data source so somebody can reproduce the observation later instead of treating a transient lookup as permanent truth.
EX
Worked example
- Resolve example.com and note every returned A/AAAA address rather than only the first.
- Check the ASN for the selected public address to understand route origination.
- Query RDAP to identify the registered network block and allocation context.
- Use GeoIP only as approximate context and record that it may reflect a POP, carrier or provider rather than the end user.
✓
Operational checklist
- Keep DNS, ASN, RDAP and GeoIP as separate evidence fields.
- Record the exact queried IP or domain and timestamp.
- Expect CDN/anycast results to vary by resolver and location.
- Never treat GeoIP city data as precise physical location.
Tools to apply it
Standards and references
🕐 History