I seem to have lost the ability to VPN into my home network from an external connection. I have a SH4, running in modem only mode, and my router is a Mikrotik RB1100AHX4. I also have a 3 UK Mobile Broadband connection (the 3 router is also in modem only mode) to the Mikrotik used as failover. Up until the last few days, I was able to connect to my home network via several VPN's I have setup on various devices. For example, I could use a travel Mikrotik Hap AC2 if I was away and an IPSec LAN to LAN connection would automatically come up and connect to home via VM. Or I could use the same HAP AC2 and use OpenVPN LAN to LAN instead of IPSec. My mobile phone was also able to connect home again via OpenVPN whilst away from home. In all circumstances, they would all be connecting via the VM primary link. However, since 2-3 days ago, I have lost the ability to connect a VPN session to home via any of the methods described above. The RB1100 logs the connection attempt but fails to complete the connection. No errors are logged during connection attempts. I am certain it's not a firewall problem because I am able to connect a VPN successfully to the RB1100 *IF* I use the 3 UK mobile connection instead. Has anything changed on the VM side? Because this issue has got me stumped!
You are correct it is my equipment (or at least my Mikrotik setup). It appears whenever the 3 Uk link is up, I cannot connect in via VM. As soon as I disabled the ethernet port to the 3 UK modem, inbound VPN works.
Why this has changed now is an altogether different question, because I have had this setup like this for well over a year and working fine.