In a split-tunnel VPN, only certain network traffic (usually traffic destined for the remote network) is sent over the VPN tunnel, while other traffic is sent directly to the local gateway and out to the internet. This can improve overall network performance for the user, but can also introduce some security risks if the local network is not properly secured.

The Network layer is responsible for logical addressing and routing, which enables data to be transmitted between different networks. It receives data from the upper layers, including the application layer, and formats it for transmission over the network by adding routing information and other protocol-specific details.

Multifactor authentication is a security measure that requires users to provide multiple pieces of evidence before they can access a network resource. This could include requiring users to enter a username, password, and a code sent to the user's mobile phone before they are allowed access. This ensures that the user is who they say they are, reducing the risk of malicious actors gaining access to network resources as a result of a successful phishing campaign.