---
title: "Mac IPv6 problems: sites hang, IPv4 works · Kilobat Guides"
url: "https://kilobat.app/guides/ipv6-problems-mac"
description: "Some sites or apps hang on a Mac while others work. Test the IPv4 and IPv6 paths apart, and turn IPv6 off only for a test."
---

IP, routing and IPv6

# IPv6 problems on a Mac

Most networks give a Mac both IPv4 and IPv6 addresses. If the IPv6 path is broken, some connections wait or fail.

Applies to: macOS 13 Ventura and later for the System Settings steps. The Terminal commands work on all current macOS versions. · Checked: 29 October 2026

## Symptoms

- Some sites or APIs hang, but others load at once.
- A tool connects after a delay, or after some retries.
- Connections work on one network but not on another network.

## Likely causes

- **A router that announces IPv6 but does not route it.** The Mac gets an IPv6 address, but traffic over IPv6 does not reach the internet.
- **A provider or VPN without full IPv6.** Some VPNs carry only IPv4. IPv6 traffic then goes outside the tunnel or fails.
- **A firewall that blocks IPv6.** A router or company firewall can block IPv6 traffic while it allows IPv4.

## How to check

1. Find the device name of each network port, for example `en0` for Wi-Fi.

   ```
   networksetup -listallhardwareports
   ```
2. Show the IPv6 addresses of the Wi-Fi interface. Addresses that start with `fe80` are link-local only.

   ```
   ifconfig en0 inet6
   ```
3. Show the router advertisement that the Mac accepted. An error means that no IPv6 router answered.

   ```
   ipconfig getra en0
   ```
4. Send pings over IPv6 to a public address.

   ```
   ping6 -c 3 2606:4700:4700::1111
   ```
5. Request a site over IPv4 only, then over IPv6 only. Compare the results.

   ```
   curl -4 -I https://www.apple.com
   ```
6. If the IPv4 request works and the IPv6 request fails, the IPv6 path is broken.

   ```
   curl -6 -I https://www.apple.com
   ```

## How to fix it

1. Restart the router. Then test again.
2. Update the router's firmware, or ask the provider about IPv6 on your line.
3. For a test, turn IPv6 off on the service.

   ```
   networksetup -setv6off Wi-Fi
   ```

   Needs an administrator password.
4. Turn IPv6 on again after the test. Use the automatic setting.

   ```
   networksetup -setv6automatic Wi-Fi
   ```

   Needs an administrator password.
5. You can also use the Configure IPv6 menu in System Settings > Network > the service > Details > TCP/IP.
6. If the problem stops only with IPv6 off, report it to the network owner or the provider.

## With Kilobat

1. `why` tries IPv4 and IPv6 apart and says which one fails.

   ```
   kilobat why api.example.com
   ```
2. The MCP tool `diagnose_connection` returns the same steps for an agent. See [Find why one site or API won't connect](https://kilobat.app/guides/recipes/why-cant-it-connect).

## Questions

**Should I keep IPv6 off?**

No. Turn it off only for a test. Ask the network owner to fix IPv6, then turn it on again.

**What is a link-local address?**

An address that starts with `fe80` works only on the local link. It does not reach the internet.

## Sources

- networksetup(8), man page installed with macOS 27.2
- ipconfig(8), man page installed with macOS 27.2
- ping6(8), man page installed with macOS 27.2
- curl(1), man page installed with macOS 27.2
- [Apple Support: Change TCP/IP settings on Mac](https://support.apple.com/guide/mac-help/change-tcp-ip-settings-on-mac-mchlp2718/mac)

Sources checked on 29 October 2026. Man pages are the ones installed with macOS; open one with `man <name>` in Terminal.

## Related guides

- [Find why one site or API won't connect](https://kilobat.app/guides/recipes/why-cant-it-connect): When the internet works but one address fails, Kilobat checks each layer in turn.
- [MTU problems on a Mac](https://kilobat.app/guides/mtu-problems-mac): The MTU is the largest packet that an interface sends.
- [VPN connected but no internet on a Mac](https://kilobat.app/guides/vpn-connected-no-internet): A VPN sends traffic through a tunnel.
- [A website works on your phone but not on your Mac](https://kilobat.app/guides/site-works-on-phone-not-mac): When a site opens on your phone but not on your Mac, the problem is usually on the Mac.