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Another strange Apple broadcast “feature”: If you try to block ARP MAC address broadcast (not IPv4 .255 type) on the router, your iPhone and MacBook will not co

Another strange Apple broadcast “feature”: If you try to block ARP MAC address broadcast (not IPv4 .255 type) on the router, your iPhone and MacBook will not connect to the WiFi. Try yourself: ebtables -A INPUT -d ff:ff:ff:ff:ff:ff -j DROP ebtables -A FORWARD -d ff:ff:ff:ff:ff:ff -j DROP (Tried on standard ASUS router by adding ebtables rules using SSH) To clean: ebtables —-flush Or restart the router, because this also flush ebtables (Edit: Corrected multicast to broadcast)

neilalexander 5y ago
That's the ethernet broadcast address, not multicast. In addition, if you block ARP, you will probably find that not very much of IPv4 anything will work on any platform.
- contingencies 5y ago
  ARP is specific to ethernet. You can still have a lot of functional point to point or other ARP-agnostic IPv4 links.
  - neilalexander 5y ago
    Indeed, but Wi-Fi is not one of those (as I was responding to).
icehawk 5y ago
They're not connecting to the WiFi because that implicitly blocks DHCPDISCOVER.
- punnerud 5y ago
  Thank you, learned something new. Can’t change the original comment now
iso1210 5y ago
I think macs can add static arp entries if you did want to disable arp for some reason. If I remember rightly, apple devices when connecting to wifi 1) Get IP, router, DNS details (either static or via dhcp) 2) Attempt to load a http page to detect any portals 3a) If page loads, is connected. 3b) If page doesn't load but redirects, pops up the portal page (in a cut down browser), then eventually connects 3c) If it doesn't load at all it asks if you want to use the wifi even with no internet access I suspect if it cant configure an IP at all (because you're blocking arp and dhcp), it doesn't fully bring the interface up. Are you saying that with a static IP entered in wifi you can't connect to a wireless network?

neilalexander 5y ago

That's the ethernet broadcast address, not multicast. In addition, if you block ARP, you will probably find that not very much of IPv4 anything will work on any platform.

contingencies 5y ago
ARP is specific to ethernet. You can still have a lot of functional point to point or other ARP-agnostic IPv4 links.
- neilalexander 5y ago
  Indeed, but Wi-Fi is not one of those (as I was responding to).

icehawk 5y ago

They're not connecting to the WiFi because that implicitly blocks DHCPDISCOVER.

punnerud 5y ago
Thank you, learned something new. Can’t change the original comment now

iso1210 5y ago

I think macs can add static arp entries if you did want to disable arp for some reason. If I remember rightly, apple devices when connecting to wifi 1) Get IP, router, DNS details (either static or via dhcp) 2) Attempt to load a http page to detect any portals 3a) If page loads, is connected. 3b) If page doesn't load but redirects, pops up the portal page (in a cut down browser), then eventually connects 3c) If it doesn't load at all it asks if you want to use the wifi even with no internet access I suspect if it cant configure an IP at all (because you're blocking arp and dhcp), it doesn't fully bring the interface up. Are you saying that with a static IP entered in wifi you can't connect to a wireless network?