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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Learn, apply and verify
Networking Guides
Practical networking guides with worked examples, diagrams and links to the calculators used in each workflow.
20 technical guides7 sections per guide20 guides with technical diagrams
IPv4 subnetting calculators and planning tools
Use this hub to move from a single IPv4 address to complete subnet plans, route summaries, ACL ranges and DHCP scopes. Each tool focuses on one networking task and links to the next logical step.
IPv4 & Subnetting ToolsVLSM step by step with a real subnet plan
Learn a repeatable VLSM method: sort requirements, choose prefixes, allocate networks and verify the final plan.
7 sections · example · checklist · diagramIPv4 & Subnetting ToolsWildcard masks for OSPF and ACLsUnderstand inverse masks, matching semantics and practical wildcard examples for routing and access-control work.
7 sections · example · checklist · diagramIPv4 & Subnetting ToolsWhen and why to use IPv4 /31 on point-to-point linksLearn why /31 is valid on point-to-point IPv4 links, what changes operationally and where it should not be used.
7 sections · example · checklist · diagramIPv4 & Subnetting ToolsSubnet overlap in VPNs and multi-site networksDiagnose overlapping RFC1918 networks, understand symptoms and plan cleaner remediation before adding NAT workarounds.
7 sections · example · checklist · diagramIPv4 & Subnetting ToolsHow to design a clean DHCP scopePlan gateways, reservations, dynamic ranges and growth capacity inside an IPv4 subnet without address collisions.
7 sections · example · checklist · diagramIPv4 & Subnetting ToolsDHCP pool exhaustion and address conflicts: diagnosis and preventionFind lease exhaustion, stale reservations, rogue DHCP servers and overlapping static ranges before users lose connectivity.
7 sections · example · checklist · diagramIPv6 addressing, prefixes and reverse-DNS tools
Work with IPv6 prefixes and notation without carrying over IPv4 assumptions. These tools cover normalization, prefix planning, transition formats, EUI-64 and ip6.arpa.
IPv6 ToolsIPv6 prefix planning without IPv4 habits
Design a simple site and VLAN hierarchy from a larger IPv6 allocation while keeping room for growth.
7 sections · example · checklist · diagramIPv6 ToolsIPv6 RA, SLAAC and DHCPv6: who configures whatUnderstand Router Advertisements, SLAAC, DHCPv6 and DNS delivery so hosts receive the expected IPv6 address, gateway and resolver information.
7 sections · example · checklist · diagramDNS, registry and network-ownership lookups
Investigate domains, addresses and network ownership from several angles: DNS answers, reverse DNS, ASN context, authoritative RDAP registration, local OUI data and approximate IP geolocation.
DNS, Registry & Lookup ToolsRDAP 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.
7 sections · example · checklist · diagramDNS, Registry & Lookup ToolsMAC randomization, OUI lookup and vendor identificationUnderstand why a valid MAC may not reveal a vendor and how 24-, 28- and 36-bit IEEE assignments differ.
7 sections · example · checklist · diagramDNS, Registry & Lookup ToolsDNS changes not propagating: TTL, cache and delegation troubleshootingSeparate authoritative data, recursive caches, TTLs and delegation mistakes when a DNS change appears correct in one place but stale elsewhere.
7 sections · example · checklist · diagramWi-Fi planning and RF calculation tools
Plan wireless channels and link budgets with channel/frequency references, free-space loss, RF power conversions and a local secure WPA passphrase generator.
Wi-Fi & RF ToolsHow to choose Wi-Fi channels in 2.4, 5 and 6 GHz
Compare channel width, overlap, DFS and PSC considerations when planning modern Wi-Fi networks.
7 sections · example · checklist · diagramWi-Fi & RF ToolsFSPL and radio link budget step by stepBuild a basic wireless link budget from transmit power, antenna gain, free-space loss and receiver sensitivity.
7 sections · example · checklist · diagramWi-Fi & RF ToolsGood Wi-Fi signal but slow throughput: what to checkDiagnose low throughput despite strong RSSI by checking airtime, retries, channel width, interference, client capability and backhaul.
7 sections · example · checklist · diagramNetwork engineering, performance and reference tools
Use this hub for day-to-day engineering tasks around MTU and tunnels, VLAN tags, multicast mappings, performance estimates, protocol references, configuration snippets and IP documentation.
Network Engineering ToolsMTU for PPPoE, GRE, WireGuard and tunnels
Work out effective MTU for common encapsulation stacks and avoid fragmentation or hidden throughput problems.
7 sections · example · checklist · diagramNetwork Engineering ToolsPMTUD and TCP MSS clamping explainedUnderstand why some sites fail across tunnels, how Path MTU Discovery works and when MSS clamping is appropriate.
7 sections · example · checklist · diagramNetwork Engineering ToolsWireGuard handshakes but no traffic: a practical troubleshooting pathTrace routes, AllowedIPs, MTU, firewall state and return paths when a WireGuard tunnel handshakes successfully but applications still fail.
7 sections · example · checklist · diagramNetwork Engineering ToolsAsymmetric routing and stateful firewalls: why valid traffic becomes INVALIDUnderstand how different forward and return paths break state tracking and how to prove the asymmetry before weakening firewall rules.
7 sections · example · checklist · diagramNetwork Engineering ToolsVLAN trunk troubleshooting: tagged, untagged and native VLAN mistakesTrace VLAN membership end to end and identify PVID, native VLAN and allowed-list mismatches that create partial or intermittent connectivity.
7 sections · example · checklist · diagramNetwork Engineering ToolsPacket loss, latency and jitter: how to isolate the real bottleneckUse controlled tests and path segmentation to separate congestion, radio errors, queueing, MTU problems and endpoint limitations.
7 sections · example · checklist · diagram
🕐 History