# Network Tools

Network tools answer questions about how devices and domains connect across the internet: which public IP address your connection uses, how a network is divided into subnets, which DNS records a domain publishes, whether email is set up to pass authentication checks, and how fast and stable your connection is.

## Subcategories

- [IP Address](https://techolm.com/network-tools/ip-address) (0 tools)
- [Subnets & Addressing](https://techolm.com/network-tools/subnets-addressing) (0 tools)
- [DNS & Domains](https://techolm.com/network-tools/dns-domains) (0 tools)
- [Email Deliverability](https://techolm.com/network-tools/email-deliverability) (0 tools)
- [Speed & Connectivity](https://techolm.com/network-tools/speed-connectivity) (0 tools)

## Tools

- What Is My IP Address (Coming soon): Show the public IPv4 and IPv6 addresses that websites see when your device connects to them.
- Subnet Calculator (Coming soon): Calculate the network address, broadcast address, host range and mask of an IPv4 subnet.
- DNS Lookup (Coming soon): Look up the A, AAAA, MX, TXT, CNAME and NS records that a domain name publishes.
- Internet Speed Test (Coming soon): Measure your download speed, upload speed and latency to a test server.

## Frequently asked questions

### What is the difference between IPv4 and IPv6?

IPv4 addresses are 32 bits long and written as four decimal numbers, such as 192.0.2.1, which allows about 4.3 billion addresses. IPv6 addresses are 128 bits long and written as hexadecimal groups separated by colons, such as 2001:db8::1, where `::` stands for a run of zero groups.

### What does /24 mean after an IP address?

It is CIDR notation: the number after the slash is how many leading bits of the address identify the network. An IPv4 /24 network has 256 addresses, and 254 of them can be assigned to devices, because the first is the network address and the last is the broadcast address.

### Why do DNS changes take time to appear?

Resolvers cache DNS answers for the time to live (TTL) set on each record, so a change becomes visible only after cached copies expire. A record with a TTL of 3,600 seconds can be cached for up to an hour. Lowering the TTL before a planned change shortens the wait.