This macOS-specific network behavior occurs due to ARP cache timeouts and incomplete network stack initialization. When Machine A attempts to ping Machine B initially, the ARP request fails silently because Machine B's network interface hasn't fully "warmed up" its network stack for inbound traffic.

The root cause lies in macOS's power-optimized network stack implementation:

• ARP cache entries expire after 1200 seconds (20 minutes) by default
• Network interfaces may enter low-power states
• Bonjour/mDNSResponder behavior differences between macOS versions

Option 1: Persistent ARP Entry (Terminal Solution)

# On Machine B (the target machine)
sudo arp -s 192.168.1.100 00:11:22:33:44:55

Option 2: Network Kernel Tuning

# Adjust ARP cache timeout (all machines)
sudo sysctl -w net.link.ether.inet.arp_ttl=3600

Option 3: Background Keepalive Script

#!/bin/bash
while true; do
  ping -c 1 -t 1 192.168.1.100 > /dev/null
  sleep 300
done

Check these critical elements when troubleshooting:

1. Run arp -a before/after successful pings
2. Compare outputs of ifconfig en0 on both machines
3. Test with tcpdump -i en0 arp running

For permanent solution, create a plist file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>local.network.keepalive</string>
    <key>ProgramArguments</key>
    <array>
        <string>/usr/bin/ping</string>
        <string>-i</string>
        <string>300</string>
        <string>-t</string>
        <string>1</string>
        <string>192.168.1.100</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
</dict>
</plist>

---

I recently encountered a bizarre networking scenario between two Mac machines (both running macOS Ventura) on the same 192.168.1.0/24 subnet:

# Initial state (before reverse ping)
Machine-A$ ping 192.168.1.101
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
...

# After Machine-B pings Machine-A
Machine-B$ ping 192.168.1.100
PING 192.168.1.100: 56 data bytes
64 bytes from 192.168.1.100: icmp_seq=0 ttl=64 time=1.234 ms

# Now Machine-A can ping Machine-B
Machine-A$ ping 192.168.1.101
PING 192.168.1.101: 56 data bytes
64 bytes from 192.168.1.101: icmp_seq=0 ttl=64 time=1.567 ms

Both machines show correct network configurations:

# Machine-A (192.168.1.100)
$ ifconfig en0
en0: flags=8863 mtu 1500
    ether aa:bb:cc:dd:ee:ff 
    inet 192.168.1.100 netmask 0xffffff00 broadcast 192.168.1.255

# Machine-B (192.168.1.101)
$ netstat -rn | grep default
default            192.168.1.1        UGSc            en0

The issue appears related to ARP cache timing out. Here's what happens:

# Before reverse ping (ARP incomplete)
$ arp -a
? (192.168.1.101) at (incomplete) on en0 ifscope [ethernet]

# After reverse ping (ARP resolved)
$ arp -a
? (192.168.1.101) at aa:bb:cc:dd:ee:ff on en0 ifscope [ethernet]

1. Adjust ARP Cache Timeout

Modify the ARP cache timeout on macOS:

# Set ARP cache timeout to 1 hour (3600 seconds)
$ sudo sysctl -w net.link.ether.inet.max_age=3600

# Make it persistent across reboots
$ echo "net.link.ether.inet.max_age=3600" | sudo tee -a /etc/sysctl.conf

2. Create Static ARP Entry

Add a permanent ARP entry:

$ sudo arp -s 192.168.1.101 aa:bb:cc:dd:ee:ff

3. Enable Periodic ARP Refresh

Create a cron job to refresh ARP periodically:

# Add to crontab (every 15 minutes)
*/15 * * * * /usr/sbin/arp -d 192.168.1.101 && /sbin/ping -c 1 192.168.1.101 >/dev/null

For application-level solutions, implement a simple keepalive:

#!/bin/bash
# keepalive.sh
while true; do
  ping -c 1 192.168.1.101 > /dev/null
  sleep 300  # Ping every 5 minutes
done

Or in Python:

import os
import time

def network_keepalive(ip, interval=300):
    while True:
        response = os.system(f"ping -c 1 {ip} > /dev/null")
        if response != 0:
            print(f"Failed to ping {ip}")
        time.sleep(interval)

network_keepalive("192.168.1.101")

If the issue persists, consider:

• Testing with different Ethernet cables
• Trying another switch/router
• Checking for NIC firmware updates