MacDebug

Verified for macOS Tahoe 26.2

Fix Guide: mDNS/Bonjour Name Resolution Failing on Tahoe

Symptom: Your Mac running macOS Tahoe cannot resolve .local hostnames (Bonjour/mDNS names) on your network. Commands like ping raspberrypi.local or ssh server.local fail with "hostname not found," but the same devices work fine with their IP addresses. Other Macs or iOS devices on the network can resolve .local names successfully.

Why this happens

macOS uses the mDNSResponder daemon to handle Bonjour/mDNS name resolution for .local domains. On Tahoe, Apple restructured mDNSResponder to separate its functions into multiple processes for security: mDNSResponder (main daemon), mDNSResponderHelper (privileged operations), and discoveryd_helper (service discovery). The inter-process communication between these services can fail if the com.apple.mDNSResponder.dnsproxy XPC service doesn't have proper network access.

Additionally, Tahoe's updated firewall (pf packet filter) may block multicast DNS traffic on UDP port 5353. The configd daemon (network configuration) can also cache stale mDNS records if it doesn't receive proper invalidation signals when network interfaces change.

Recommended Troubleshooting Tool

Before proceeding with manual fixes, we recommend using CleanMyMac X. Quickly identify high CPU apps and optimize system memory with one click.

- [Download CleanMyMac X Free Here](#)

- [Browse 240+ Premium Mac Utilities on Setapp](#)

Fix 1: Restart mDNSResponder and Clear DNS Cache

Reset Bonjour services and flush all DNS caches:

# Stop mDNSResponder
sudo killall -HUP mDNSResponder

# Clear DNS cache
sudo dscacheutil -flushcache

# Clear mDNS-specific cache
sudo killall -9 mDNSResponder
sudo killall -9 mDNSResponderHelper

# Restart network configuration daemon
sudo killall configd

# Wait for services to restart automatically
sleep 5

# Test mDNS resolution
dns-sd -G v4 device-name.local

# Try pinging a known .local device
ping device-name.local

Fix 2: Check and Fix Firewall/Network Settings

Ensure multicast DNS traffic isn't blocked:

# Check if firewall is blocking mDNS (port 5353 UDP)
sudo pfctl -s rules | grep 5353

# Add firewall rule to allow mDNS if blocked
sudo pfctl -e
echo "pass in proto udp from any to any port 5353" | sudo pfctl -f -

# Check network interface for multicast routing
netstat -g

# Verify mDNS multicast address (224.0.0.251) is present
# If not, reset network interfaces:
sudo ifconfig en0 down
sudo ifconfig en0 up

# For Wi-Fi, get the interface name first
networksetup -listallhardwareports

# Reset Wi-Fi (replace "Wi-Fi" with your actual service name)
sudo networksetup -setv6off Wi-Fi
sudo networksetup -setv6automatic Wi-Fi

# Restart NetworkManager
sudo launchctl unload /System/Library/LaunchDaemons/com.apple.networkd.plist 2>/dev/null
sudo launchctl load /System/Library/LaunchDaemons/com.apple.networkd.plist

Fix 3: Rebuild Network Configuration and mDNS Database

Reset network configuration files:

# Backup existing network configuration
sudo cp -R /Library/Preferences/SystemConfiguration ~/Desktop/SystemConfiguration-backup

# Remove network configuration cache
sudo rm /Library/Preferences/SystemConfiguration/NetworkInterfaces.plist
sudo rm /Library/Preferences/SystemConfiguration/preferences.plist

# Remove mDNS responder state
sudo rm -rf /var/run/mDNSResponder
sudo rm /Library/Preferences/com.apple.mDNSResponder.plist

# Remove DNS proxy state
sudo rm -rf /var/run/dnsproxy

# Force recreation of network services
sudo launchctl unload /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist 2>/dev/null
sudo launchctl load /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist

# Reboot to fully reinitialize network stack
sudo reboot

After reboot, go to System Settings → Network and verify your network connection is active.

Recommended Tool: **Discovery - DNS-SD Browser**

Discovery (available on Mac App Store) is a comprehensive Bonjour/mDNS browser that helps diagnose network service discovery issues. It shows all advertised services on your network, including .local hostnames, with real-time updates. You can see exactly which devices are broadcasting mDNS announcements and which your Mac is successfully receiving. Discovery also displays detailed service information (port numbers, TXT records, priority) and allows you to test connectivity to discovered services. If Discovery can see a .local device but your Terminal commands can't resolve it, that indicates a DNS resolver configuration issue rather than a network problem. The app is invaluable for troubleshooting mDNS on Tahoe.