L2TPv3 – Intro
Table of content
Intro Top
You can configure L2TPv3 in 3 Modes.
Manual Mode
Manual Mode with Keep Alive
Dynamic Mode
Manual Mode is where you manually specify the session characteristics on both sides of the session ie no session negotiation takes place.
Configurable components of L2TPv3 are : Top
xconnect
Pseudowire-class
l2tp-class xconnect
xconnect Top
The xconnect command is configured under the interface to bind the attachment circuit to the pseudowire session. The syntax is as follows:-
xconnect peer-ip vcid pseudowire-paramaters [sequencing {transmit | receive both}]
The peer ip address is usually the loopback address of the remote PE. The vcid is a 32 bit virtual circuit identifier and should match on both sides of the pseudowire. There are two options for the pseudowire-paramaters you can configure define encapsulation or use a pw-class (see examples of both below)
xconnect 3.3.3.3 100 encapsulation l2tpv3
xconnect 3.3.3.3 100 pw-class ZARAR
The pw-class is a mandatory argument when l2tpv3 manual mode is used as the encapsulation method.
sequencing {transmit | receive both}
This is an optional argument that is used primarily when configuring l2tpv3 in manual mode. If sequencing is enabled then out of order packets are dropped.
Pseudowire-class Top
The pseudowire inherits the session characteristics defined in the Pseudowire-class. To define a Pseudowire-class use the commands below:
Pseudowire-class [Pseudowire-class-name]
Once you enter this mode, the CLI drops you into a pw-class configuration mode. In this mode the following configuration options are available.
encapsulation Top – Defines the tunneling method. Initially this is the only command available to the user as the other options listed below depend on the encapsulation type.
ip local interface interface Top name – defines the source of the l2tpv3 control and data packets.
protocol {l2tpv3|none} [l2tp-class-name] Top – defines whether l2tpv3 is used for session negotiation (For manual mode the protocol is none)
sequencing {transmit | receive both} Top – same as described above
ip dfbit set Top – Sets the dfbit for the IP Packet header of the l2tpv3 packets.
ip pmtu Top – enables the discovery of PMTUD
ip tos Top {value value | reflect} – set the ip tos for the IP Packet header of the l2tpv3 packets. reflect copies the TOS of the payload IP packet to the P Packet header of the l2tpv3 packets.
ip ttl value Top – sets the ip ttl for the IP Packet header of the l2tpv3 packets.
ip protocol {l2tp|uti} - Top allows interoperability with UTI.
l2tp-class Top
The l2tp-class defines the session characteriscts for the control channel. The l2tp-class is referenced in the Pseudowire-class. To define a l2tp-class use the commands below:
l2tp-class [l2tp-class name]
Once you enter this mode, the CLI drops you into a l2tp-class configuration mode. In this mode the following configuration options are available.
Top- option is either to send a 4 or 8 byte cookie. by default cookie length is zero.
timeout setup Top – time permitted to setup the control channel
authentication Top – enables CHAP-like authentication between peers
hostname Top – used to identify the local device in chap authentication. By default router hostname name is used.
password Top- preshared secret.
Top – used to hide sensitive AVPs.
hello Top- defines the keepalive interval once control channel is setup. The default is 60Seconds.
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