Cisco IOS Wide-Area Networking Configuration Guide - Free Books

For simple L2TPv3 signaling configurations on most platforms, pseudowire class configuration isoptional. However, specifying a source IP address to configure a loopback interface is highlyrecommended. If you do not configure a loopback interface, the router will choose the best availablelocal address, which could be any IP address configured on a core-facing interface. This configurationcould prevent a control channel from being established. On the Cisco 12000 series Internet routers,specifying a source IP address is mandatory, and you should configure a loopback interface that isdedicated for the use of L2TPv3 sessions exclusively. If you do not configure other pseudowire classconfiguration commands, the default values are used.Once you specify the encapsulation l2tpv3 command, you cannot remove it using the no encapsulationl2tpv3 command. Nor can you change the command's setting using the encapsulation mpls command.Those methods result in the following error message:Encapsulation changes are not allowed on an existing pw-class.To remove the command, you must delete the pseudowire with the no pseudowire-class command. Tochange the type of encapsulation, remove the pseudowire with the no pseudowire-class command andre-establish the pseudowire and specify the new encapsulation type.SUMMARY STEPS1. enable2. configure terminal3. pseudowire-class [pw-class-name]4. encapsulation l2tpv35. protocol {l2tpv3 | none} [l2tp-class-name]6. ip local interface interface-name7. ip pmtu8. ip tos {value value | reflect}9. ip dfbit set10. ip ttl value11. ip protocol {l2tp | uti | protocol-number}12. sequencing {transmit | receive | both}DETAILED STEPSStep 1Step 2Command or ActionenableExample:Router> enableconfigure terminalPurposeEnables privileged EXEC mode.• Enter your password if prompted.Enters global configuration mode.Example:Router# configure terminal59