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. Rather than having competing protocols for tunneling, the internet engineering task force ietf asked the two companies to work together to combine. The layer 2 tunneling protocol l2tp is a standard protocol for tunneling l2. 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. L2f does not provide encryption or confidentiality by itself. This document describes the transport of ethernet frames over the layer 2 tunneling protocol, version 3 l2tpv3. Several features enable the l2tp mgmt daemon process within cisco ios software, including but not limited to layer 2 virtual private networks l2vpn, layer 2 tunnel protocol version 3 l2tpv3, stack group bidding protocol sgbp and cisco virtual private dialup networks vpdn. L2tp is defined in rfc 2661, layer two tunneling protocol l2tp. Rfc 7886 was draftietfl2tpextsbfddiscriminator advertising seamless bidirectional forwarding detection sbfd discriminators in the layer two tunneling protocol version 3 l2tpv3. Many of these protocols are originally based on the internet protocol suite tcpip and other models and they often do. L2tp vpn everything about layer 2 tunneling protocol. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Layer 2 protocol tunneling l2pt is achieved by encapsulating the pdus at the ingress pe device before transmitting them over the service provider network. The layer 2 protocol tunnel port is configured through cli commands.
L2tp is similar to the data link layer protocol in the osi reference model, but it is actually a session layer protocol. Layer 2 tunneling protocol l2tp l2tp extends the ppp model by allowing the l2 termination point network access server or lac l2tp access concentrator and ppp endpoint lns l2tp network server to reside on different devices interconnected by an ip network. 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. Some ssl vpn products have the capability to combine various. Develop a complete rfc3931 compliant l2tpv3 implementation for posix compliant operating systems. Layer 2 protocol tunnel porta port on the edge switch on which a specific tunneled protocol can be encapsulated or deencapsulated. L2f was specifically designed to tunnel pointtopoint protocol ppp traffic. Tunneling methods are differentiated based upon the type of tunneling protocol used to encapsulate data. Recently, microsoft and cisco agreed to merge their respective protocols into a single, standard protocol called layer two tunneling protocol l2tp an ietf and industrystandard layer 2 tunneling solution. Additional documents detail the specifics for each data link. L2tp is a tunneling solution that combines the advantages of pptp pointto point tunneling protocol and l2f layer 2 forwarding. Advantages and disadvantages of l2tp best vpn services.
Layer 2 control protocol peering, forwarding, and tunneling. Download layer 2 tunneling protocol version 3 for free. Configuring layer 2 protocol tunneling this chapter describes how to configure layer 2 protocol tunneling in cisco ios software release 12. Each group state represents the result of a merging process applied to subscriptions on l2tp sessions. Layer 2 protocol tunneling ccie cisco certified expert. Specifically, l2tpv3 defines the l2tp protocol for tunneling layer 2. Signaling of modemonhold status in layer 2 tunneling protocol l2tp.
Pdf implementation of ipsecvpn tunneling using gns3. The layer 2 protocol, such as ethernet, will also include a reference to which layer 3 protocol has been used and a checksum to ensure data integrity. Wheeler doublewide software august 2002 layer two tunneling protocol l2tp management information base status of this memo this document specifies an internet standards track protocol for the internet community, and requests discussion and. Then l2tp becomes an access protocol to the new ltm service. The user has an l2 connection to an access concentrator, which then tunnels. To use l2tp in windows server 2003, you must have a public key infrastructure pki to issue computer certificates to the virtual private network vpn server and to clients so that the internet key exchange ike authentication process can occur. The vulnerability is due to insufficient validation of l2tp packets. Layer two tunneling protocol l2tpv3, internet protocol. Once this process is enabled the device is vulnerable. L2tpv3 is the successor to the cisco proprietary implementation of universal tunnel interface uti for layer 2 tunneling and implementation of layer 2 vpns. 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 truth is, l2tp is a tunneling protocol and doesnt provide any form of encryption by itself. To an lac, the ltm service appears as an lns, to an lns the ltm service appears as an lac. An enni frame with a destination mac address shown in table b is defined to be a layer 2 control protocol enni frame. Layer 2 tunneling protocol l2tp is an advanced networking protocol that is used to support vpn services. Cisco layer 2 forwarding l2f and layer 2 tunneling protocol l2tp are also.
Layer two tunneling protocol l2tp management information. Rfc 4719 transport of ethernet frames over layer 2. Instead, a new l2tp tunnel merging and management service ltm service is created. Securing layer two tunneling protocol l2tp with internet. 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 2 tunneling protocol version 3 thelayer2tunnelingprotocolversion3featureexpandsciscossupportoflayer2vpns. Additional ways of denoting a layer 2 control protocol enni frame at a given enni can be agreed to by the two. L2tpv3 accounts for signaling capabilities that were not implemented in the initial uti implementations. Technical documentation this feature is supported on the following productsapplications. An ipsec transformation set is configured in the routers to combine the authentication. Bridge layer 2 protocol tunneling cumulus networks. L2f is part of the layer 2 tunneling protocol l2tp standard rfc 2661.
It is a combination of the two protocols, the pptp of microsoft and the layer 2 forward l2f of cisco. Defines l2tp avp attributes 53 modem onhold capable and 54 modem onhold status. Layer 2 protocols 3 31 layer 2 protocols 3 pptp point to point tunneling protocol pptp ppp ip encapsulation for tcpip, ipx, and netbeui no encryption, but extended with rc4, pap, chap, and eap singlefactor authentication. Layer 2 protocol tunneling can be used independently or to enhance 802. This list is not exclusive to only the osi protocol family.
Layer 2 tunneling protocol l2tp ipsec extensions intellectual property rights notice for open specifications documentation technical documentation. It relies on the protocol being tunneled to provide privacy. Ethernet switching and bridging layer 2 protocol tunneling l2pt layer 2 protocol tunneling l2pt more information about this feature. Layer two tunneling protocol l2tp is an extension of the pointtopoint tunneling. L2tp provides a transparent communication between the two endusers and applications across the intervening network.
Vpn concept and runs with it, employing l2tp to merge two or more lans. Layer 2 tunneling protocol l2tp is a computer networking protocol used by internet service providers isps to enable virtual private network vpn operations. Result of merging ciscos l2f layer 2 forwarding protocol and. This document describes version 3 of the layer two tunneling protocol l2tpv3. Short for layer 2 tunneling protocol, l2tp is a tunneling, session layer protocol, using the udp port 1701 on a vpn virtual private network. Us6094437a layer two tunneling protocol l2tp merging. A layer two tunneling protocol l2tp is an extension of pptp protocol. When protocol tunneling is enabled, layer 2 protocols within each. Layer 2 and layer 3 tunneling involve the use of tunneling protocols that correspond to the data link layer and the network layer. The layer 2 tunneling protocol l2tp allows the transmission of frames between two nodes. The encapsulation prevents the pdus from being processed by the switches in the sp network. After the process is complete, the l2tp packets between the endpoints are encapsulated by ipsec.
Multicast traffic in layer2 tunneling protocol l2tp. A tunnel is not encrypted by default, it relies on the tcpip protocol chosen to determine the level of security. Layer two tunneling protocol l2tp specifies multiprotocol access via pointtopoint protocol ppp. The mechanism described in this document can be used in the creation of pseudowires to transport ethernet frames over an ip network. Layer 2 tunneling protocol l2tp l2tp is the internet engineering task force ietf standard layer 2 tunneling protocol that was designed to merge the best features of l2f and pptp. Layer two tunneling protocol extensions l2tpext documents. L2tpv3 overview implementing vpns with layer 2 tunneling. Microsoft supports l2tp in windows 2000xp client software for clientinitiated vpn tunnels.
L2f, or layer 2 forwarding, is a tunneling protocol developed by cisco systems, inc. It is also possible to establish a connection using the data link layer. Gtacknowledge layer two layer 2 protocol packets does. How to bridge private two lan bridge lans over the internet.
Pointtopoint communication protocol and pptp point to point tunneling protocol. Ppp that merges features of two tunneling protocols. L2tp abbreviation stands for layer2 tunneling protocol. My old actiontec router failed and it was replaced with a new model m1424wr. A user datagram protocol udp port is used for l2tp. This includes the transport of ethernet porttoport frames as well as the transport of ethernet vlan frames. L2tp 8 is an open source layer 2 tunneling 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.
Layer two forwarding l2f is a cisco tunneling protocol that uses virtual dialup networks for secure data packet transport. The pervious router was set up for port forwarding and it worked with out any problems i am running a mac server os 10. L2tp offers the best performance and scalability of the three. A vxlan connects layer 2 domains across a layer 3 fabric. Layer two tunneling protocol l2tp is an extension of the pointtopoint tunneling protocol used by an internet service provider to enable the operation of a virtual private network over the internet. The lac sits between an lns and a remote system and forwards packets to and from each. Layer 2 tunneling protocol l2tp active discovery relay for ppp over ethernet pppoe. 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. Microsoft publishes open specifications documentation this documentation for protocols, file formats, data portability, computer languages, and standards support. What is the abbreviation for layer2 tunneling protocol. 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.
L2f functionality is similar to the pointtopoint tunneling protocol pptp, which was developed by the microsoftled pptp forum. The fips 14027 specification defines how cryptographic modules will be. L2tp is one of the most widely used protocol to create a vpn connection between your device and a remote vpn server. Pdf virtual private networks vpn provide remotely secure connection for.
Cisco ios and ios xe software layer 2 tunneling protocol. It does not include any encryption and relies on other methods to provide data security and privacy, such as ipsec. L2tp merges the best features of two other tunneling protocols. 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. L2tpv3 defines the base control protocol and encapsulation for tunneling multiple layer 2 connections between two ip nodes. Point tunneling protocol l2tp layer 2 tunnel protocol sstp secure socket tunneling protocol open.
A common misconception is that l2tp is an encryption protocol. It combines the features of pptp and ciscos l2f protocols. Advantages and disadvantages of l2tp layer 2 tunneling protocol l2tp is a combination of the earlier microsoft pointtopoint tunneling protocol pptp and cisco systems layer 2 forwarding. Rfc 3931 layer two tunneling protocol version 3 l2tpv3. This article discusses how to configure a preshared key for use with layer 2 tunneling protocol l2tp.
Note for complete syntax and usage information for the commands used in this chapter, see the cisco ios software releases 12. The layer 2 tunneling protocol l2tp launched in 1999 is an update on the point to point tunneling protocol pptp. Operation there are two steps to tunneling a ppp session with l2tp 1 establishing a control. Pdf technical overview of virtual private networksvpns. 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 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 provide a. 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. It does not provide any encryption or confidentiality by itself. So when im outside my house i can connect to the server from anot. Rfc 4045 extensions to support efficient carrying of multicast. 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.
An attacker could exploit this vulnerability by sending a crafted l2tp packet to an affected device. This article lists protocols, categorized by the nearest layer in the open systems interconnection model. It was originated primarily from two different tunneling protocols, named as. Cisco ios software layer 2 tunneling protocol l2tp.
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