IP Addresses
Your Mac has one address at home and shows another to the internet. This explains public and private addresses, IPv4 and IPv6, NAT and DHCP, and how to see yours in Netutilus for Mac.
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Every device on a network has an IP address, the number other devices send to. There are two kinds that matter day to day.
Private and public
- Private addresses exist only inside your network, such as 192.168.1.24, 10.0.0.5 or 172.16.0.8. Your router hands them out, and every home uses the same ranges, so they mean nothing outside it. Network Monitor and LAN Scanner show them.
- The public address is the one your provider gives your router. All the devices in your home share it on the internet, the router keeping track of which reply belongs to whom (that’s NAT). The menu bar item and GeoIP show it.
A VPN replaces your public address with its own, which is how it hides you. See Is my VPN working?
IPv4 and IPv6
IPv4 addresses are four numbers, such as 93.184.216.34. There aren’t enough of them for every device, which is why homes share one. IPv6 addresses are longer, such as 2606:2800:220:1::248, and plentiful enough that each device can have its own. Many networks run both. Plenty still run only IPv4, and that’s fine.
Addresses that tell you something
- 127.0.0.1 is the Mac itself.
- 169.254.x.x means the Mac asked for an address and the router never answered. Restarting the router usually fixes it.
- 100.64.x.x to 100.127.x.x as your public address means your provider shares one public address among many customers (carrier-grade NAT).
Related
- Subnets and CIDR, how addresses are grouped.
- DNS, which turns names into addresses.
Run it on your own network
Netutilus puts every network tool in one app. Free to download; Pro is a one-time purchase, never a subscription.
More in learn
- BufferbloatWhy the delay shoots up while your line is busy, and how to fix it on the router.
- CertificatesHow a website proves who it is, and why a connection sometimes isn't trusted.
- DNSThe internet's address book, which turns names like example.com into addresses.
- Hops and TTLHow traffic crosses the internet one router at a time, and how traceroute finds each one.
- ICMP and TCP PingTwo ways to time a host, and why one may answer when the other doesn't.
- JitterHow much the delay changes from one moment to the next, and why calls and games care.