VPN

A VPN (Virtual Private Network) is a dedicated connection to a LAN (Local Area Network) via the internet. When connected via a VPN connection, a Local Area Network is not restricted by the limitations regarding physical cables, and the local network can therefore connect to the internet through a VPN client.

VPNs can be typically characterized as host-to-network or remote access by connecting a single computer to a network or as site-to-site for connecting two networks.

Common tunneling protocols

• IP in IP (Protocol 4): IP in IPv4/IPv6
• SIT/IPv6 (Protocol 41): IPv6 in IPv4/IPv6
• GRE (Protocol 47): Generic Routing Encapsulation
• OpenVPN (UDP port 1194): Openvpn
• SSTP (TCP port 443): Secure Socket Tunneling Protocol
• IPSec (Protocol 50 and 51): Internet Protocol Security, IKEv1 and IKEv2 modes). Tunnel and transport modes.
• L2TP (Protocol 115): Layer 2 Tunneling Protocol
• VXLAN (UDP port 4789): Virtual Extensible Local Area Network.

Cisco IOS: show vpn

• show vpn flow
• show vpn gateway
• show vpn ike-sa
• show vpn ipsec-sa
• show vpn tunnel

See Also

• Ipsec, OpenVPN and WireGuard implementations
• ReviewsDir: VPN Beginner's Guide
• PAN-OS: show vpn flow
• AAA Servers, such as RADIUS, LDAP or Active Directory (AD)
• Cisco PIX