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
Data stored in your browser
Theme, language, promotion dismissal and calculation history are stored in localStorage on this device.
Calculations
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.
Issue reports via Telegram
A report link opens the public Telegram bot and includes only the current page slug in the bot start parameter. Calculator inputs and report text are not sent by this website. Text you choose to send inside Telegram is handled by Telegram and the bot.
Cookies and advertising
Advertising is controlled by the production configuration. When Google AdSense is enabled, consent is handled through a certified CMP before personalized advertising is used where required.
Delete local data
Use the button below to clear calculation history. To remove every local preference, clear this site's data in your browser settings.
This page provides operational information; it is not a legal-compliance certification.
IPv6 RA, SLAAC and DHCPv6: who configures what
Understand Router Advertisements, SLAAC, DHCPv6 and DNS delivery so hosts receive the expected IPv6 address, gateway and resolver information.
01
Router Advertisements provide the default-router signal
IPv6 hosts learn on-link prefixes and default-router information from Router Advertisements. DHCPv6 does not replace this default-router role, so a host can receive an address from DHCPv6 and still have broken connectivity if RA is missing or filtered.
02
SLAAC builds addresses from advertised prefixes
With the autonomous flag, hosts can construct addresses from a /64 prefix without a stateful address server. Privacy extensions may create temporary addresses, so inventory should not assume a single stable interface identifier.
03
Managed and Other flags guide host behavior
RA flags can tell clients to use DHCPv6 for addresses or for additional information, but exact client behavior varies by operating system. Validate Windows, Linux, Android and embedded clients rather than assuming one policy behaves identically everywhere.
04
DNS delivery is a separate design choice
Resolvers can arrive through DHCPv6, RDNSS in RA, local policy or platform-specific mechanisms. A host with a valid IPv6 address and default route can still look “offline” to users if name resolution was never delivered.
05
Do not block essential ICMPv6 while “hardening”
Neighbor Discovery, Router Advertisements and Path MTU feedback depend on ICMPv6. Blanket filtering can leave hosts with partial connectivity that looks like random IPv6 failure.
06
Use packet capture to see what the host actually receives
An RA capture reveals prefix, flags, lifetime and often DNS information. That is faster than inferring configuration from the final address alone.
07
Plan stable addressing and privacy separately
Servers and infrastructure may need predictable addresses while user devices benefit from temporary privacy addresses. Use address policy appropriate to each role instead of forcing one model everywhere.
EX
Worked example
- Capture an RA on the client VLAN and verify the advertised /64 and router lifetime.
- Check whether the A/M/O flags match the intended SLAAC/DHCPv6 design.
- Verify the client receives a default route and DNS information by the chosen mechanism.
- Test IPv6 name resolution and a large HTTPS flow so routing and PMTUD are both exercised.
✓
Operational checklist
- RA reaches the client VLAN.
- Advertised prefix is the intended /64.
- Default-router lifetime is non-zero when routing is expected.
- DNS delivery mechanism is verified per client OS.
- Essential ICMPv6 is permitted.
Tools to apply it
Standards and references
🕐 History