Internet protocol security, or IPSec, is a protocol used for several purposes, one of them being VPNs. It operates at the the network level as opposed to the application level (used by SSL). What’s it used for? IPSec is often paired with other VPN protocols like L2TP …

Layer 2 Control Protocol Peering, Forwarding, and Tunneling SUMMARYSTEPS 1. enable 2. configureterminal 3. interfacetypenumber 4. l2proto-forwardtaggedprotocol 5. serviceinstanceidethernet 6. encapsulationuntagged 7. l2protocolforward[protocol] 8. bridge-domainbridge-id 9. xconnectpeer-ip-addressvc-idencapsulationmpls DETAILEDSTEPS CommandorAction Purpose Step1 enable EnablesprivilegedEXECmode. Example: … Session Layer | Layer 5 | The OSI-Model An example of a session-layer protocol is the OSI protocol suite session-layer protocol, also known as X.225 or ISO 8327. In case of a connection loss this protocol may try to recover the connection. If a connection is not used for a long period, the session-layer protocol may close it and re-open it. Port 1701 (tcp/udp) :: SpeedGuide

L2F or Layer 2 Forwarding is a tunneling protocol developed by Cisco Systems. It is used to build virtual private networks (VPNs) over the internet that could in turn …

L2TP over the Internet - L2TP VPN tutorial L2TP (Layer 2 Tunneling Protocol) L2TP is an extension of the PPTP (Point to point tunneling protocol), used by internet service providers to provide VPN services over the internet. L2TP combines the functionality of PPTP and L2F (Layer 2 forwarding protocol) with some additional functions using some of the IPSec functionality.

Published in 2000 as proposed standard RFC 2661, L2TP has its origins primarily in two older tunneling protocols for point-to-point communication: Cisco's Layer 2 Forwarding Protocol (L2F) and Microsoft's Point-to-Point Tunneling Protocol (PPTP). A new version of this protocol, L2TPv3, appeared as proposed standard RFC 3931 in 2005.

What Is a Virtual Private Network? Technologies and Protocols Used to Enable Remote Access VPNs Protocols used to enable remote access VPNs (discussed later in this chapter) include the following: • The Layer Two Forwarding (L2F) Protocol—L2F is a Cisco proprietary protocol that is designed to allow the tunneling of PPP (or Serial Line Interface Protocol [SLIP]) VPN Tunnels L2F L2TP 3 normal (non-tunnel) encapsulation * 2 PPPoE 2 3 inner packet layer outer packet layer 2 tunneling layer 3 tunneling •IP in Ethernet •IP in PPP, or •UDP or TCP in IP •HTTP in TCP •DNS in UDP *examples: Uses of tunneling Bridge protocols over domain where they are illegal Bridge addresses over domain where they are illegal Layer 2 Control Protocol Peering, Forwarding, and Tunneling SUMMARYSTEPS 1. enable 2. configureterminal 3. interfacetypenumber 4. l2proto-forwardtaggedprotocol 5. serviceinstanceidethernet 6. encapsulationuntagged 7. l2protocolforward[protocol] 8. bridge-domainbridge-id 9. xconnectpeer-ip-addressvc-idencapsulationmpls DETAILEDSTEPS CommandorAction Purpose Step1 enable EnablesprivilegedEXECmode. Example: … Session Layer | Layer 5 | The OSI-Model