Free Network Utilities & Firewall Tools | IP, VLSM, CIDR & More

Online Network Utilities: IP, VLSM, CIDR Calculators & Converters

NetTools is a collection of online utilities for network engineers and administrators: IPv4 subnet calculation, VLSM planning, CIDR route summarization, firewall rule splitting, bandwidth calculator, password generator, IP/MAC converters, and number base converter. All tools run directly in your browser.

All Utilities

Select the tool you need — all available services are listed below.

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IP Calculator (IPv4 Subnet Calculator)

Calculate subnet parameters by IP address/mask or CIDR: network address, broadcast address, host range, and total number of addresses. Perfect for quick subnet validation.

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IP Converter

Convert IPv4 addresses into binary and hexadecimal formats. Useful for bitwise checks, ACL configuration, and documentation.

Convert IP →
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VLSM Calculator

Design address plans with variable-length subnets. Quickly allocate networks based on the required number of hosts.

Calculate VLSM →
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Password Generator

Generate secure passwords for network devices, Wi-Fi, servers, and other systems. Adjustable complexity options available.

Generate Password →
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dBm ↔ mW Calculator

Convert signal power values for RF, wireless, and optical networking calculations. Useful for link budget analysis.

Convert dBm →
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CIDR Aggregator (Route Summarization)

Aggregate multiple IP subnets into the minimal set of summarized routes. Helps optimize routing tables.

Aggregate Networks →
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Bandwidth Calculator

Calculate data transfer speed, download time, and convert between Mbps and MB/s. Useful for link capacity planning.

Calculate →
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MAC Address Converter

Convert MAC addresses between colon, dash, and dot formats. Useful for documentation and device lookup.

Convert MAC →
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Number Base Converter (DEC/BIN/HEX)

Quickly convert between decimal, binary, and hexadecimal number systems.

Convert Numbers →
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Firewall Rule Splitter

Subtract selected SRC-DST-SERVICE flows from the allowed set and generate minimal safe firewall rules.

Open Splitter →
⚙️ Online tools for network professionals: VLSM calculator online, IP subnet calculator, IP address converter, CIDR summarization, firewall rule splitter, bandwidth calculator, password generator, MAC address converter, dBm to mW, DEC/BIN/HEX converter.

FAQ Frequently Asked Questions

What is CIDR and why use a CIDR Aggregator?
CIDR (Classless Inter-Domain Routing) represents subnets using prefix notation, such as 192.168.10.0/24. A CIDR Aggregator helps summarize multiple subnets into fewer routes to simplify routing.
How is VLSM different from standard subnetting?
VLSM allows creation of subnets with different sizes within the same address block by selecting prefixes based on host requirements, optimizing address space usage.
IP Calculator vs IP Converter?
The IP Calculator computes subnet parameters, while the IP Converter translates IPv4 addresses into binary or hexadecimal formats.
What is the difference between Mbps and MB/s?
Mbps stands for megabits per second, while MB/s stands for megabytes per second. 1 byte equals 8 bits. 100 Mbps ≈ 12.5 MB/s.
Why use a dBm ↔ mW calculator?
It converts signal power values for RF, wireless, and optical networking tasks. dBm is logarithmic, while mW is linear.
Why use a MAC converter?
To standardize MAC address formats (colons, dashes, dots) for filtering, configuration, and documentation.
What does Firewall Rule Splitter do?
It removes selected SRC-DST-SERVICE flows from an allowed rule space and produces a compact set of resulting rules. This helps reduce manual firewall edits and avoid over-permissive policies.

NetTools PRO Network Utilities — all services available on a single page. Suitable for both beginners and experienced network engineers. Fully online, no installation required, completely free.