macOS Sequoia network issues

Problem Solved! - And an alternative Solution for Network Issues on Macs with Sequoia 15.0.1 (Intel Chip)

Hey everyone,

I wanted to share a workaround and the latest update on an issue we ran into recently with some Macs at our company. We have around 15 Macs, and they were all working fine until a few days ago, when we started seeing frequent, frustrating network issues:

• Random disconnections from our internal software
• Email failures
• DNS resolution issues (resulting in no internet connection)

Here’s what I found:

After looking closely at the differences between the Macs having issues and those that weren’t, I realized the problem only affected iMacs that were:

• Updated to Sequoia 15.0.1
• Running on Intel chips

Meanwhile, iMacs running Sequoia on M1 or M2 chips or those on Sonoma (Intel, M1, or M2) were working perfectly.

Troubleshooting Steps Tried (Spoiler: Didn’t Work)

I tried everything I could think of: replacing cables, configuring devices with DHCP, setting Fixed IPs, assigning IPs based on MAC addresses, adding IPs and DNS into our firewall, disabling firewalls and VPNs, and fiddling with advanced Ethernet settings. Nothing seemed to work.

Temporary Fix (Before the final solution)

While troubleshooting, I managed to identify a way to reproduce the issue: simply rebooting an affected iMac. After a reboot, it wouldn’t immediately connect due to (what I think it is)a bug in the “mDNSResponder” process, which affected auto-discovery and server detection.

To work around this, I wrote a script to:

1. Detect the active Ethernet interface
2. Shut it down temporarily, then turn it back on after 10 seconds.

#!/bin/bash

# List all active network interfaces
for interface in $(networksetup -listallhardwareports | awk '/Device:/{print $2}')
do
  # Get IP address assigned to the interface
  ip=$(ifconfig $interface | awk '/inet /{print $2}')

  # If IP address is assigned, print the interface and the IP
  if [ -n "$ip" ]; then
    echo "Ethernet Interface: $interface"
    echo "IP Address: $ip"
    # Turn off the interface
	sudo ifconfig $interface down
    # Wait for 10 seconds
	sleep 10
    # Turn the interface back on
	sudo ifconfig $interface up   
  fi
done

Running this script daily helped keep our iMacs connected – not a pretty solution, but it worked.

The Real Fix (Finally!)

Yesterday, I noticed that Apple released Sequoia 15.1. I updated one of the affected iMacs last night, and today it’s been working perfectly. After several reboots, the problem hasn’t resurfaced, which looks promising!

I’ll be updating the rest of our affected iMacs at the earliest opportunity and will report back if there are any hiccups.

Hope this helps! If this solution worked for you or you found this useful, please upvote so others can find it easily.

Thanks!

Junior.