Layer 2 and layer 3 tunneling involve the use of tunneling protocols that correspond to the data link layer and the network layer in the open system interconnection osi model. Layer 2 tunneling protocol l2tp ipsec extensions intellectual property rights notice for open specifications documentation technical documentation. When l2tpv3 is implemented, the physical interfaces that are connected to the customers network are used as tunnel ingress and egress interfaces. Bridge layer 2 protocol tunneling cumulus networks. L2tp combines the best features of ciscos layer 2 forwarding l2f and microsofts pointtopoint tunneling protocol pptp, enabling mobile workforces to connect to their corporate intranets or extranets wherever and whenever they require. Rather, it relies on an encryption protocol that it passes within the tunnel to provide privacy. L2tp merges the best features of two other tunneling protocols. Layer two tunneling protocol l2tp is an extension of the pointtopoint tunneling protocol pptp used by an internet service provider isp to enable the operation of a virtual private network vpn over the internet. Supported shared port adapters for cisco asr series routers. Configuring support for layer 2 protocol tunneling. In computer networking, layer 2 tunneling protocol l2tp is a tunneling protocol used to published in as proposed standard rfc, l2tp has its origins primarily in two older tunneling protocols for pointtopoint. L2tpv2 tunneling of ppp feature overview and configuration. A vulnerability in the layer 2 tunneling protocol l2tp parsing function of cisco ios and cisco ios xe software could allow an unauthenticated, remote attacker to cause an affected device to reload.
Tunneling protocol an overview sciencedirect topics. Layer 2 tunneling protocol wikipedia, a enciclopedia livre. Layer two tunneling protocol l2tp specifies multi protocol access via pointtopoint protocol ppp. Vpn is a virtual private network that allows a user to connect to a private network over the internet securely and privately. Abstract this document describes the layer two tunneling protocol l2tp. L2tp stands for layer 2 tunneling protocol, and its like the name implies a tunneling protocol that was designed to support vpn connections. L2tp provides a transparent communication between the two endusers and applications across the intervening network. Rfc 2661 layer two tunneling protocol l2tp rfc2661.
So l2tp is a tunneling protocol used to support vpn or part of the delivery of services by isps, not provide any encryption or confidentiality by it. What does layer 2 tunneling protocol actually mean. The lac sits between an lns and a remote system and forwards packets to and from each. Rfc 3931 layer two tunneling protocol version 3 l2tpv3. L2f functionality is similar to the pointtopoint tunneling protocol pptp, which was developed by the microsoftled pptp forum. It is also possible to establish a connection using the data link layer. Nov 14, 2019 virtual private network technology is based on the concept of tunneling. If you disable layer 2 protocol tunneling on a port, the disabled protocols function the same way they were functioning before layer 2 protocol tunneling was disabled on the port.
Layer 2 tunneling protocol l2tp is a computer networking protocol used by internet service providers isps to enable virtual private network vpn operations. Just like a water pipe contains the liquid flowing inside of it, a vpn tunnel insulates and encapsulates internet trafficusually with some type of encryptionto create a private tunnel of data as it flows inside an unsecured network. Internet assigned numbers authority iana considerations update. The layer two tunneling protocol l2tp provides a dynamic mechanism for tunneling layer 2 l2 circuits across a.
Edge switchthe switch connected to the customer switch and placed on the boundary of the service provider network see figure 211. Layer 2 protocol tunneling allows layer 2 protocol data units pdus cdp, stp, and vtp to be tunneled through a network. The layer 2 tunneling protocol l2tp launched in 1999 is an update on the point to point tunneling protocol pptp. Layer 2 tunneling protocols, such as pptp and l2tp, use frames. Mar 24, 2020 a vxlan connects layer 2 domains across a layer 3 fabric. Layer to tunneling protocol offers data encryption through ipsec protocol. Cisco ios and ios xe software layer 2 tunneling protocol.
Without layer 2 protocol tunneling, tunnel ports dr op stp and vtp packets and process cdp packets. It was designed as a sort of successor to pptp, and it was developed by both microsoft. Pdf encapsulation of mpls over layer 2 tunneling protocol. Like pptp, it uses a single pointtopoint connection per session. These protocols divide the message into different parts usually two. Its ability to carry almost any l2 data format over ip or other l3 networks makes it. L2tpv3 layer two tunneling protocol version 3 is a pointtopoint layer two over ip tunnel. In computer networks, a tunneling protocol is a communications protocol that allows for the movement of data from one network to another. The layer 2 tunneling protocol l2tp allows the transmission of frames between two nodes. This can be pretty usefulfor example, lets say you have two remote sites and an application that requires that hosts are on the same subnet.
Std 51, rfc 1661 specifies multiprotocol access via ppp rfc1661. Virtual private networks washington university in st. An ietf standard protocol for creating virtual private networks. In other words, l2tp layer 2 tunnel protocol is an upandcoming ietf internet engineering task force standard that came in front with the traits of two onhand tunneling protocols. The layer 2 tunneling protocol, version 3 l2tpv3 defines a protocol for tunneling a variety of payload types over ip networks. Pointtopoint tunneling protocol pptp is a set of communication rules that govern the secure implementation of virtual private networks vpn, which allow organizations a method of extending their own private networks over the public internet via tunnels. A layer two tunneling protocol l2tp is an extension of pptp protocol.
Securing layer two tunneling protocol l2tp with internet protocol security ipsec is a standard that explains to users how l2tp may utilize ipsec to provide for tunnel authentication, privacy protection, integrity checking and replay protection. Dtp untagged peer peerforward tunnel lacp untagged peer peerforward tunnel lldp untagged peer peerforward tunnel stp untagged peer peerforward tunnel vtp untagged peer peerforward tunnel cdp tagged drop forward tunnel. Harmening, in computer and information security handbook third edition, 2017. Layer 2 control protocol peering, forwarding, and tunneling. Layer 2 tunneling protocol l2tp l2tp is an emerging ietf standard and one of the key building blocks for vpns in the dial access space. Layer two tunneling protocol extensions l2tpext documents. Layer 2 tunneling protocol version 3 restrictions for layer 2 tunneling protocol version 3 3 convergence at bootup or rp switchover takes a significant amount of time depending on the number of configured session.
Pointtopoint communication protocol and pptp point to point tunneling protocol. By using pptp, a large organization with distributed offices can create a large. L2tp is defined in rfc 2661, layer two tunneling protocol l2tp. Additional documents detail the specifics for each data link type being emulated. L2tp is an open standard with mutlivendor interoperability and acceptance. Vpn 21 l2tp layer 2 tunneling protocol rfc 2661 no control channel user makes dialupppp to local acess concentrator local phone calls access concentrator redirects ppp frames to isp via internet.
My study of this paper is based on layer 2 tunneling protocol. Rfc 7886 was draftietfl2tpextsbfddiscriminator advertising seamless bidirectional forwarding detection sbfd discriminators in the layer two tunneling protocol version 3 l2tpv3. Layer two tunneling protocol l2tp created 200303 last updated 20160715 note unless otherwise noted, the registrations in this registry are applicable in the context of the ietf vendor id. It does not include any encryption and relies on other methods to provide data security and privacy, such as ipsec. How to bridge private two lan bridge lans over the internet. The layer 2 tunneling protocol l2tp is a standard protocol for tunneling l2 traffic over an ip network.
L2tpv3 defines the base control protocol and encapsulation for tunneling multiple layer 2 connections between two ip nodes. Layer 2 tunneling protocol l2tp is a hybrid of pptp and layer 2 forwarding l2f. Types of vpn and types of vpn protocols vpn one click. Layer two tunneling protocol l2tp, august canonical url. Layer 2 tunneling protocol version 3 thelayer2tunnelingprotocolversion3featureexpandsciscossupportoflayer2vpns. Cisco ios software layer 2 tunneling protocol l2tp denial. Advantages of layer to tunneling protocol l2tp there are different advantages associated with layer to tunneling protocol that proves it to be a better alternative as compared to pptp. If you disable layer 2 protocol tunneling on a port, the disabled protocols function the same way they were functioning before layer 2 protocol tunneling was enabled on the port. Layer two tunneling protocol article about layer two.
What is the abbreviation for layer 2 tunneling protocol. A user datagram protocol udp port is used for l2tp. The pdu is then flooded to the native vlan of the layer 2 tunnel port. L2tpv2 layer 2 tunneling protocol l2tpv2 enables encapsulated layer 2 frames to be carried across the network. In this paper, we will focus on l2tp layer 2 tunneling protocol which is basically introduce to deploy. Within the discussion of content networking, we will. Rfc 3438 layer two tunneling protocol l2tp internet assigned numbers. Funnily enough, l2tp is often employed by isps to allow vpn operations.
Point tunneling protocol l2tp layer 2 tunnel protocol sstp secure socket tunneling protocol. Rfc 3573 signaling of modemonhold status in layer 2 tunneling protocol l2tp rfc 3817 layer 2 tunneling protocol l2tp active discovery relay for ppp over ethernet pppoe. Tunneling methods are differentiated based upon the type of tunneling protocol used to encapsulate data. If you want the vxlan to behave more like a wire or hub, where protocol packets are tunneled instead of being terminated locally, you can enable bridge layer 2 protocol tunneling. The vulnerability is due to insufficient validation of l2tp packets. Download layer 2 tunneling protocol version 3 for free. Layer 2 vpn architectures is a comprehensive guide to consolidating network infrastructures and extending vpn services. Layer 2 tunneling protocol in computer networking, layer 2 tunneling protocol l2tp is a tunneling protocol used to support virtual private networks vpns. Tunneling protocols are especially difficult because from the perspective of the user of the tunnel they are a link layer protocol but from the perspective of the network carrying the tunnel they are an application or transport layer protocol tcpip doesnt really have presentation or session layers. L2tpv3 provides the capabilities to tunnel layer 2 payload over ip network. For l2tpv2 these l2 frames are pointtopoint protocol ppp layer 2 frames. Us6094437a layer two tunneling protocol l2tp merging and.
Layer two tunneling protocol l2tpv3, internet protocol. Layer 2 tunneling protocol version 3 amolak networks. Defines l2tp avp attributes 53 modem onhold capable and 54 modem onhold status. Short for layer 2 tunneling protocol, l2tp is a tunneling, session layer protocol, using the udp port 1701 on a vpn virtual private network. Develop a complete rfc3931 compliant l2tpv3 implementation for posix compliant operating systems. Pdf an increase in the size and requirements of a mobile workforce is. In computer networking, layer 2 tunneling protocol l2tp is a tunneling protocol used to support virtual private networks vpns or as part of the delivery of services by isps. Layer 2 tunneling protocol l2tp active discovery relay for ppp over ethernet pppoe. L2tp abbreviation stands for layer 2 tunneling protocol. Vpn creates an encrypted connection, known as vpn tunnel, and all internet traffic and communication is passed through this secure tunnel. A system is provided for creating a tunneling service from the use of a traditional tunneling protocol, such as the layer two tunneling protocol l2tp.
It really is a layer 5 protocol because it uses the session layer in the osi. L2tp is similar to the data link layer protocol in the osi reference model, but it is actually a session layer protocol. An attacker could exploit this vulnerability by sending a crafted l2tp packet to an affected device. Signaling of modemonhold status in layer 2 tunneling protocol l2tp. Enable layer 2 protocol tunneling l2pt on a vlan on switches that do not use the the enhanced layer 2 software els configuration style which includes ex2200, ex3300, ex4200, ex4500, and ex4450 switches. A tunnel is not encrypted by default, it relies on the tcpip protocol chosen to determine the level of security. Packets sent from the lac to the lns requires tunneling with the l2tp protocol as defined in this document. In particular, the l2tp tunneling protocol, which is designed to go pointtopoint between an l2tp access concentrator lac and an l2tp network server lns, is abstracted so that l2tp becomes an access protocol to a tunneling service. One containing the actual data being transmitted, and one containing information regarding the rules of the transmission.
Layer 2 protocol tunneling ccie cisco certified expert. L2tp facilitates the tunneling of ppp packets across an intervening network in a way that is as transparent as possible to both endusers and applications. Ipsec protocol maximizes your security and prevents all unauthorized access. Information that flows over the internet, or between any two digital devices, does so using protocols. Find out inside pcmags comprehensive tech and computerrelated encyclopedia. If you enable layer 2 protocol tunneling on a port, pdus of an enabled protocol are not sent out. Layer 2 tunneling protocol l2tp a tunneling protocol used to support virtual private networks vpns or as part of the delivery of services by isps. Published in 1999 as proposed standard rfc 2661, l2tp has its origins primarily in two older tunneling protocols for ppp. L2tpv2 enables pointtopoint ppp frames to be totally encapsulated within network. Microsoft publishes open specifications documentation this documentation for protocols, file formats, data portability, computer languages, and standards support. It uses the same authentication mechanisms as pptp but its tunneling protocol is advanced as it relies on ipsec for encryption. Many of these protocols are originally based on the internet protocol suite tcpip and other models and they often do not fit neatly into osi layers. L2f is part of the layer 2 tunneling protocol l2tp standard rfc 2661.
Layer 2 tunneling protocol how is layer 2 tunneling. Layer 2 tunneling protocol ssl certificate management site. Specifies the layer 2 tunneling protocol l2tp ipsec extensions, which allows ip, ipx, or netbeui traffic to be encrypted and then sent over any medium that supports pointtopoint ppp point to point protocol rfc1661 datagram delivery, such as ip, x. Specifically, l2tpv3 defines the l2tp protocol for tunneling layer 2. The layer 2 tunneling protocol l2tp is an internet engineering task force ietf standard protocol that allows ip, ipx, or netbeui traffic to be encrypted, and then sent over any medium that supports pointtopoint ppp datagram delivery, such as ip, x. For example, stp for a vlan on switch 1 see figure 271 builds a spanning tree. It combines the features of pptp and ciscos l2f protocols. Layer 2 forwarding protocol l2f da cisco e o pointtopoint tunnelling protocol pptp da microsoft. This document describes version 3 of the layer two tunneling protocol l2tpv3. It does not include any encryption and relies on other methods to provide data security and privacy, such as ipsec l2tp can be used as a tunneling mechanism to resell adsl connectivity by cable providers and by companies who.
Apr 01, 2020 the layer 2 tunneling protocol l2tp launched in 1999 is an update on the point to point tunneling protocol pptp. Rfc 2661 l2tp august 1999 l2tp access concentrator lac a node that acts as one side of an l2tp tunnel endpoint and is a peer to the l2tp network server lns. A standard protocol for tunneling l2 traffic over an ip network 5. This handling of the pdus creates different spanning tree domains different spanning tree roots for the customer switches. Mar 10, 2018 layer 2 protocol tunneling can be used independently or to enhance 802. Palter redback networks august 1999 layer two tunneling protocol l2tp status of this memo this document specifies an internet standards track protocol for the internet community, and requests discussion and. This means you can tunnel l2 protocols like ethernet, framerelay, atm, hdlc, ppp, etc.
Aug 18, 2011 layer 2 tunneling protocol l2tp is a computer networking protocol used by internet service providers isps to enable virtual private network vpn operations. It involves allowing private network communications to be sent across a public network such as the internet through a process called encapsulation. It was originated primarily from two different tunneling protocols, named as. Layer 2 tunneling protocol wikimili, the best wikipedia. L2tp is one of the most widely used protocol to create a vpn connection between your device and a remote vpn server. For example, a network layer 3 packet encapsulates a transport layer 4 packet, and a data link layer 2 packet encapsulates a network layer 3 packet. A new version of this protocol, l2tpv3, was published as proposed standard rfc 3931 in 2005. The book opens by discussing layer 2 vpn applications utilizing both atom and l2tpv3 protocols and comparing layer 3 versus layer 2 providerprovisioned vpns. In addition to describing the concepts related to layer 2 vpns, this book provides an extensive. Documented in rfc2661, l2tp and rfc3931, l2tpv3 are protocols for tunneling network traffic between two peers over an existing network a device running affected 12. In computer networking, layer 2 tunneling protocol l2tp is a tunneling protocol used to support virtual private networks vpns or as part of the delivery of. Layer two forwarding l2f is a cisco tunneling protocol that uses virtual dialup networks for secure data packet transport. It is a combination of the two protocols, the pptp of microsoft and the layer 2 forward l2f of cisco. Securing layer two tunneling protocol l2tp with internet.
Ciscos layer 2 forwarding protocol l2f and us robotics pointtopoint tunneling protocol pptp. The radius feature overview and configuration guide. This article lists protocols, categorized by the nearest layer in the open systems interconnection model. Layer 2 tunneling protocol overview techlibrary juniper.
After the process is complete, the l2tp packets between the endpoints are encapsulated by ipsec. L2tp vpn everything about layer 2 tunneling protocol. Rfc 2661 layer two tunneling protocol l2tp ietf tools. Layer two tunneling protocol l2tp over frame relay. Find out information about layer two tunneling protocol. It does not provide any encryption or confidentiality by itself. This list is not exclusive to only the osi protocol family.
986 85 710 607 141 1492 1556 362 327 1129 1337 1100 1014 37 938 133 1110 935 955 1152 904 1364 1263 86 593 1466 1021 29 914 989 1367