Apple iOS updates fail with `no internet connectivity' at verification

[hkirschk]

My home network is protected by a opnsense installation containing some basic firewall rules, mainly allowing everything on connecting LAN to WAN and blocking almost all for WAN to LAN. My iPhone/iPad are connected via some Ubiquiti WiFi APs. All connections work for web surfing, email etc. The only problem I have is about iOS updates, for those I always get that `no internet connectivity' message when verifying the update image. It works when I switch off the WiFi connection and use the mobile connection for verification. Does anyone have an idea what can be done to allow for iOS update verifications passing the opnsense firewall? I found no hints what could be wrong, Apple states that the ports to their servers have to be open, which is the case for the standard rules as I assume.

Anyone any ideas on that?

Update 2019-10-17: This issue had nothing to do with firewall rules. After setting the WAN MTU to 1468 (i.e., a bit less than the default of 1500), everything worked fine.

[packet loss]

I have several apple products connected to my wireless network. I use an ASUS RT-AC3100 as an AP. I never have any issues updating my Apple software or firmware. Seems like your firewall rules are too strict. Good luck.