The network layer is responsible for routing and forwarding packets through the network. The issue here suggests successful authentication but routing failure. Troubleshooting should focus on IP addressing, routing protocols, or access control lists at this layer.

Configuring split tunneling allows users to access local network resources while connected to the VPN. It provides flexibility in routing local traffic directly and only sending necessary data through the VPN tunnel. This approach balances local resource access and VPN security.

VLANs reduce the size of broadcast domains by segmenting the network logically, isolating broadcast traffic within each VLAN. This process helps improve overall network performance and efficiency. VLANs provide both enhanced security and reduced broadcast-related bottlenecks.

VLAN Trunking Protocol (VTP) is used for the management and synchronization of VLAN information across switches. VTP provides consistent VLAN configuration across a network. It reduces the complexity of VLAN management and ensures the efficiency of configuration updates.

Encapsulation Security Payload (ESP) in IPSec provides the necessary encryption and encapsulation to protect the packet’s data and payload. It delivers confidentiality, integrity, and authenticity for encapsulated packets. ESP ensures a VPN secures data traversing public networks.

SSL VPNs usually establish secure remote connections using the TLS protocol. Since SSL has been replaced by TLS for securing remote web connections, using TLS is essential for strong and current security protocols. This ensures secure remote network access over the Internet.

AH (Authentication Header) in IPSec provides data integrity and packet authenticity without performing encryption. It is typically used when data confidentiality is not required but authenticity is essential. AH verifies methods and content, ensuring data is not tampered with.

Ensuring VTP version compatibility is key to VLAN synchronization across networks. An incompatible VTP version or mode can result in VLAN configuration mismatches and failures. Correct VTP configuration works to distribute and manage VLAN information efficiently.

Tunneling encapsulates packets of one protocol type into another protocol type, allowing them to effectively traverse different types of networks. This technique is crucial for transmitting IP packets across non-IP networks or for VPNs to secure and carry data efficiently.

Verifying the VTP (VLAN Trunking Protocol) domain name consistency on the backup switch allows it to synchronize the VLAN topology. VTP helps manage VLAN additions, deletions, and name changes across the network. Inconsistencies in the VTP domain name can lead to synchronization failures.