---
title: "Mac MTU problems: pages hang, small requests work · Kilobat Guides"
url: "https://kilobat.app/guides/mtu-problems-mac"
description: "Small requests work but large pages, uploads or VPN traffic stall on a Mac. Find the largest packet that passes and set the MTU."
---

IP, routing and IPv6

# MTU problems on a Mac

The MTU is the largest packet that an interface sends. If a link in the path takes only smaller packets, large transfers can stall.

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 start to load, then stop.
- Small requests work, but uploads or large downloads stall.
- Problems start only with a VPN on, or only on one network.

## Likely causes

- **A link with a smaller MTU.** PPPoE, VPN tunnels and some mobile links carry smaller packets than standard Ethernet, which uses 1500 bytes.
- **Blocked ICMP messages.** A firewall that blocks ICMP can stop the Mac from learning that a packet is too large.
- **A manual MTU setting.** A value set by hand can be too large or too small for this network.

## How to check

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

   ```
   networksetup -listallhardwareports
   ```
2. Show the MTU of the interface.

   ```
   networksetup -getMTU en0
   ```
3. Send a ping of 1472 data bytes with the Don't Fragment bit set. With 28 header bytes, it makes 1500 bytes.

   ```
   ping -D -s 1472 -c 3 1.1.1.1
   ```
4. If no replies come back, try smaller sizes. Find the largest size that gets replies, then add 28.

   ```
   ping -D -s 1464 -c 3 1.1.1.1
   ```
5. Show the MTU values that the interface accepts.

   ```
   networksetup -listValidMTURange en0
   ```

## How to fix it

1. Change the MTU only on the advice of your provider or administrator, or after the test above.
2. Choose Apple menu > System Settings > Network. Click the service, click Details, then click Hardware.
3. Set Configure to Manual, then enter the MTU.
4. Or set it in Terminal. This example uses 1492, a common value for PPPoE.

   ```
   networksetup -setMTU en0 1492
   ```

   Needs an administrator password.
5. To go back to the automatic MTU, use this command.

   ```
   networksetup -setMTUAndMediaAutomatically en0
   ```

   Needs an administrator password.
6. For a VPN, change the MTU in the VPN app, if it has this setting.

## Questions

**Why does 1472 give 1500?**

An IPv4 ping packet has a 20-byte IP header and an 8-byte ICMP header. 1472 data bytes plus 28 header bytes make 1500.

**Why 1492 for PPPoE?**

PPPoE adds its own header inside an Ethernet frame. RFC 2516 limits the PPPoE MRU to 1492 bytes.

## Sources

- networksetup(8), man page installed with macOS 27.2
- ping(8), man page installed with macOS 27.2
- [Apple Support: Change Hardware settings on Mac](https://support.apple.com/guide/mac-help/change-hardware-settings-on-mac-mchlp2505/mac)
- [RFC 2516: A Method for Transmitting PPP Over Ethernet (PPPoE)](https://www.rfc-editor.org/rfc/rfc2516)

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

## Related guides

- [IPv6 problems on a Mac](https://kilobat.app/guides/ipv6-problems-mac): Most networks give a Mac both IPv4 and IPv6 addresses.
- [VPN connected but no internet on a Mac](https://kilobat.app/guides/vpn-connected-no-internet): A VPN sends traffic through a tunnel.
- [SSH and Git time out on a Mac](https://kilobat.app/guides/ssh-git-timeouts): SSH and Git need a working TCP connection to the server.
- [See Mac network settings in Terminal](https://kilobat.app/guides/network-settings-terminal): macOS includes command-line tools that show the same network settings as System Settings, and more.