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 $
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FSPL and radio link budget step by step
Build a basic wireless link budget from transmit power, antenna gain, free-space loss and receiver sensitivity.
01
Build the budget from gains and losses
A basic link budget starts with transmit power, adds transmit-antenna gain, subtracts feeder losses and free-space path loss, then adds receive-antenna gain. The result is an estimated receive level.
02
Compare receive level with sensitivity
Receiver sensitivity depends on modulation, channel width and hardware. The difference between predicted receive power and the sensitivity required for the target rate is the theoretical fade margin.
03
FSPL is only the ideal propagation term
Buildings, vegetation, Fresnel obstruction, polarization errors, rain at high frequencies, multipath and interference can all reduce real performance even when the free-space calculation looks comfortable.
04
Design for margin, not just connectivity
A link that barely clears sensitivity on a spreadsheet can become unstable with weather, alignment drift or interference. Production links need deliberate margin and monitoring.
05
Fresnel clearance belongs beside the dB arithmetic
Even with line of sight, objects inside the first Fresnel zone can introduce diffraction loss. Long links need enough physical clearance around the direct path, not only visual visibility between antennas. Terrain profile and mounting height therefore belong in the same design review as FSPL.
06
Target modulation changes the required margin
Receiver sensitivity becomes less forgiving as modulation and channel width increase. Designing only for “link up” can yield unstable high-rate service; select a target MCS or throughput class and compare the expected receive level with the corresponding sensitivity.
07
Validate alignment and interference after installation
Real received signal, noise floor, SNR, retries and modulation should be compared with the budget. A large difference between predicted and measured levels often points to alignment, cable loss, polarization, obstruction or an incorrect antenna gain assumption.
EX
Worked example
- Assume 20 dBm transmit power, 16 dBi TX antenna gain and 1 dB feeder loss.
- Subtract the calculated FSPL for the chosen frequency and distance, then add the RX antenna gain and subtract RX feeder loss.
- Compare the resulting receive level with the receiver sensitivity for the target modulation; the difference is your theoretical fade margin.
- After installation, compare measured RSSI/SNR with the budget and investigate any large unexplained deficit.
✓
Operational checklist
- Use real frequency, distance and antenna gains.
- Check Fresnel clearance and polarization, not only line of sight.
- Design for target modulation with deliberate fade margin.
- Compare the prediction with live RSSI, SNR, retries and MCS after installation.
Tools to apply it
Standards and references
🕐 History