Difference In routing behaviour between Android and iOS

[red321]

Hi,

Been running OpenVpn back to my home LAN from both an android phone and an iPad, using the clients. When I moved from 1 hotel to another I lost access to my home LAN from the iPad, but the android phone still worked. I tracked it down (eventually) to the fact that the hotel hotspot address ranges overlapped my home LAN in the second location but not the first.

So I have a Home DSL router, with a Ubuntu Server on the LAN running Openvpn-as with :

HomeLan 192.168.1.0/24
OpenVPN 172.27.232.0/20
Hotspot/hotel Whatever ..........

I am using a routed solution, with NAT fromthe172 VPN to the HomeLan, and default routing to the HomeLan router for Internet access.

So when the Hotspot/Hotel/Remote network is not 192.168.1.0/24 then both the clients can connect, access services on the home LAN and connect to the internet, all through the tunnel, taking their DNS via the HomeLan DSL router.

It was on the second WIFI network with a 192.168.1.0/24 subnet that I got odd behaviour.

I was confused by the fact I had Internet access and DNS, but no LAN access on the ipad, turns out that the WIFi LAN the iPad is on has the same default router settings ( and router by coincidence) as my home LAN, so all 192.168.1.0/24 destined traffic, including DNS was routing locally, rather than over the tunnel, so homeLAN server access was failing, as they were locally routing, DNS was also going by the local router and succeeding as was Internet traffic over the tunnel.

Android device works differently ( what I want ), with all traffic going over the tunnel.

Is this a "feature" ? I can understand arguments for both behaviours. Is there a way to force iOS behaviour to match android ?

I have restored access to the tunnel for all traffic on the iPad by changing the LAN address on the iPad to a static /32, rather than the /24 allocated by the DHCP of the hotel router. But Iam intrigued to understand if this is a feature of iOS or the client itself. iOS is a bit of a black box, as I cant easily see routing tables etc.

[Traffic]

It is called a "routing conflict" .. and the best thing you can do is change your Home LAN subnet to something more unique and also RFC1918 compliant. f.e 172.23.45.0/24