Question: What is the difference between VPN and VPN pass-through feature on router?
VPN feature on router means that router supports the VPN technology natively, such as IPsec, PPTP or L2TP. You can configure this router to act as VPN server or establish site-to-site VPN with other VPN gateway.
Then what is VPN pass-through feature on router? Well, this type of router does not support VPN technology natively, it will only allow the VPN traffic that initiated from VPN client to pass through to Internet, then reach the remote VPN gateway. This feature is commonly found on home wired/wireless router that supports hide NAT or PAT (only need 1 public IP to access Internet from home network).
Due to the complexity of VPN technology, the VPN pass-through feature must be enabled on home router if you try to establish VPN back to your company VPN gateway by using company notebook. Most of the routers would support these pass-through features:
VPN pass-through for IPSec
VPN pass-through for PPTP
VPN pass-through for L2TP