I currently have 2 ER605 Routers connected Via IPSec VPN for access to both networks 192.168.11.0/24 and 192.168.21.0/24. There is nothing wrong with the current configuration. 

Only issue I have is devices on either subnet do not see MAC addresses. I would like to know what is required to allow for any devices on either network to see one another's MAC Address. (There is multiple reasons for needing to do so) 

I read that it may be required to switch to L2TP or maybe use the 10.x.x.x / 172.16.x.x Subnet but nothing with a direct answer. Before modifying settings I wanted to check here. 

Thanks!