Cisco IOS Multiprotocol Label Switching Configuration Guide, Release 12.2SR

L2VPN: Pseudowire Preferential Forwarding

The L2VPN: Pseudowire Preferential Forwarding feature allows you to configure pseudowires so that you can use ping, show, and traceroute commands to find status information of the pseudowires before, during, and after a switchover.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for L2VPN: Pseudowire Preferential Forwarding" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for L2VPN: Pseudowire Preferential Forwarding

•Restrictions for L2VPN: Pseudowire Preferential Forwarding

•Information About L2VPN: Pseudowire Preferential Forwarding

•How to Configure L2VPN: Pseudowire Preferential Forwarding

•Configuration Examples for L2VPN: Pseudowire Preferential Forwarding

•Additional References

•Feature Information for L2VPN: Pseudowire Preferential Forwarding

Prerequisites for L2VPN: Pseudowire Preferential Forwarding

•Before configuring the L2VPN: Pseudowire Preferential Forwarding feature, you should understand the concepts in the following documents:

–Preferential Forwarding Status Bit Definition (draft-ietf-pwe3-redundancy-bit-xx.txt)

–MPLS Pseudowire Status Signaling

–L2VPN Pseudowire Redundancy

–NSF/SSO—Any Transport over MPLS and AToM Graceful Restart

–MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV

•The provider edge (PE) routers must be configured with the following features:

–L2VPN Pseudowire Redundancy

–NSF/SSO—AToM and AToM Graceful Restart

•The L2VPN: Pseudowire Preferential Forwarding feature requires that the following mechanisms be in place to enable you to detect a failure in the network:

–LSP Ping/Traceroute and Any Transport over MPLS Virtual Circuit Connection Verification (AToM VCCV)

–Local Management Interface (LMI)

–Operation, Administration, and Maintenance (OAM)

Restrictions for L2VPN: Pseudowire Preferential Forwarding

•Only ATM attachment circuits are supported.

•The following features are not supported:

–Port mode cell relay

–Any Transport over MPLS: AAL5 over MPLS

–VC cell packing

–OAM emulation

–Integrated LMI/permanent virtual circuit (PVC)-D

–PVC Range

–L2TPv3 Pseudowire Redundancy

–Local switching

–Multiple backup pseudowires

–Static pseudowires

Information About L2VPN: Pseudowire Preferential Forwarding

The following section provides information about the L2VPN: Pseudowire Preferential Forwarding feature:

•Overview of L2VPN: Pseudowire Preferential Forwarding

Overview of L2VPN: Pseudowire Preferential Forwarding

The L2VPN: Pseudowire Preferential Forwarding feature allows you to configure pseudowires so that you can use ping, show, and traceroute commands to find status information before, during, and after a switchover. The implementation of this feature is based on Preferential Forwarding Status Bit Definition (draft-ietf-pwe3-redundancy-bit-xx.txt). The L2VPN: Pseudowire Preferential Forwarding feature provides these enhancements for displaying information about the pseudowires:

•You can issue ping mpls commands on the backup pseudowires.

•You can display status of the pseudowires before, during, and after a switchover, using the show xconnect and show mpls l2transport vc commands.

Note In a single-segment pseudowire, the PE routers at each end of the pseudowire serve as the termination points. In multisegment pseudowires, the terminating PE routers serve as the termination points.

How to Configure L2VPN: Pseudowire Preferential Forwarding

The following section explains how to configure the L2VPN: Pseudowire Preferential Forwarding feature:

•Configuring the Pseudowire (required)

Configuring the Pseudowire

You configure a connection, called a pseudowire, between the routers to transmit Layer 2 frames between PE routers.

As part of the pseudowire configuration, issue the status redundancy master command to make it the master. This enables the L2VPN: Pseudowire Preferential Forwarding feature to display the status of the active and backup pseudowires. By default, the PE router is in slave mode.

Note One pseudowire must be the master and the other must be assigned the slave. You cannot configure both pseudowires as master or slave.

Note You must specify the encapsulation mpls command as part of the pseudowire class for the Any Transport over MPLS (AToM) VCs to work properly. If you omit the encapsulation mpls command, you receive the following error:
% Incomplete command.

Prerequisites

The PE routers must be configured for the L2VPN Pseudowire Redundancy and NSF/SSO—Any Transport over MPLS and AToM Graceful Restart features. See the following documents for configuration instructions:

•L2VPN Pseudowire Redundancy

•NSF/SSO—Any Transport over MPLS and AToM Graceful Restart

SUMMARY STEPS

1. enable

2. configure terminal

3. pseudowire-class name

4. encapsulation mpls

5. status redundancy {master | slave}

6. interworking {ethernet | ip}

DETAILED STEPS

Configuration Examples for L2VPN: Pseudowire Preferential Forwarding

This section contains the following examples:

•L2VPN: Pseudowire Preferential Forwarding Configuration: Example

•Displaying the Status of the Pseudowires: Example

L2VPN: Pseudowire Preferential Forwarding Configuration: Example

The following commands configure a PE router with the L2VPN: Pseudowire Preferential Forwarding feature:

mpls ldp graceful-restart

mpls ip

mpls label protocol ldp

mpls ldp router-id Loopback0 force

mpls ldp advertise-labels

!

pseudowire-class mpls

 encapsulation mpls

 status redundancy master

interface ATM0/2/0.1 multipoint

 logging event subif-link-status

 atm pvp 50 l2transport

  xconnect 10.1.1.2 100 encap mpls 

   backup peer 10.1.1.3 100 encap mpls

end

Displaying the Status of the Pseudowires: Example

The following examples show the status of the active and backup pseudowires before, during, and after a switchover.

The show mpls l2transport vc command on the active PE router displays the status of the pseudowires:

Router# show mpls l2transport vc

Local intf     Local circuit              Dest address    VC ID      Status    

-------------  -------------------------- --------------- ---------- ----------

AT0/2/0.1      ATM VPC CELL 50            10.1.1.2         100        UP        

AT0/2/0.1      ATM VPC CELL 50            10.1.1.3         100        STANDBY   

The show mpls l2transport vc command on the backup PE router displays the status of the pseudowires. The active pseudowire on the backup PE router has the HOTSTANDBY status.

Router-standby# show mpls l2transport vc

Local intf     Local circuit              Dest address    VC ID      Status    

-------------  -------------------------- --------------- ---------- ----------

AT0/2/0.1      ATM VPC CELL 50            10.1.1.2         100        HOTSTANDBY

AT0/2/0.1      ATM VPC CELL 50            10.1.1.3         100        DOWN      

During a switchover, the status of the active and backup pseudowires changes:

Router# show mpls l2transport vc

Local intf     Local circuit              Dest address    VC ID      Status    

-------------  -------------------------- --------------- ---------- ----------

AT0/2/0.1      ATM VPC CELL 50            10.1.1.2         100        RECOVERING

AT0/2/0.1      ATM VPC CELL 50            10.1.1.3         100        DOWN      

After the switchover is complete, the recovering pseudowire shows a status of UP:

Router# show mpls l2transport vc

Local intf     Local circuit              Dest address    VC ID      Status    

-------------  -------------------------- --------------- ---------- ----------

AT0/2/0.1      ATM VPC CELL 50            10.1.1.2         100        UP        

AT0/2/0.1      ATM VPC CELL 50            10.1.1.3         100        STANDBY   

The show xconnect command displays the standby (SB) state for the backup pseudowire, which is independent of the stateful switchover mode of the router:

Router# show xconnect all

Legend:    XC ST=Xconnect State  S1=Segment1 State  S2=Segment2 State

  UP=Up       DN=Down            AD=Admin Down      IA=Inactive

  SB=Standby  HS=Hot Standby     RV=Recovering      NH=No Hardware

XC ST        Segment 1                                  S1 Segment 2                                  
S2

------+---------------------------------+--+---------------------------------+---------

UP pri ac   AT1/1/0.1/1/1:220/220(ATM V  UP mpls 10.193.193.3:330            UP

IA sec ac   AT1/1/0.1/1/1:220/220(ATM V  UP mpls 10.193.193.3:331            SB

The ping mpls and traceroute mpls commands show that the dataplane is active on the backup pseudowire:

Router# ping mpls pseudowire 10.193.193.22 331

%Total number of MS-PW segments is less than segment number; Adjusting the segment number 
to 1

Sending 5, 100-byte MPLS Echos to 10.193.193.22,

     timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

  'L' - labeled output interface, 'B' - unlabeled output interface,

  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,

  'P' - no rx intf label prot, 'p' - premature termination of LSP,

  'R' - transit router, 'I' - unknown upstream index,

  'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms

Router# traceroute mpls pseudowire 10.193.193.22 331 segment 1

Tracing MS-PW segments within range [1-1] peer address 10.193.193.22 and timeout 2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

  'L' - labeled output interface, 'B' - unlabeled output interface,

  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,

  'P' - no rx intf label prot, 'p' - premature termination of LSP,

  'R' - transit router, 'I' - unknown upstream index,

  'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

! 1 10.193.33.22 4 ms [Labels: 23 Exp: 0]

    local 10.193.193.3 remote 10.193.193.22 vc id 331

Additional References

The following sections provide references related to the L2VPN: Pseudowire Preferential Forwarding feature.

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for L2VPN: Pseudowire Preferential Forwarding

Table 1 lists the release history for this feature.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

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Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.

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