Configuring EoMPLS Layer 2 VPN Graceful Restart

This chapter describes how to configure Label Distribution Protocol (LDP) Graceful Restart (GR) for the Ethernet over MPLS (EoMPLS) Layer 2 VPN Graceful Restart feature.

This chapter includes the following sections:

Finding Feature Information

Your software release might not support all the features documented in this module. For the latest caveats and feature information, see the Bug Search Tool at https://tools.cisco.com/bugsearch/ and the release notes for your 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 “New and Changed Information” chapter or the Feature History table below.

Information About EoMPLS Layer 2 VPN Graceful Restart

This section includes the following topics:

EoMPLS Layer 2 VPN Graceful Restart

The EoMPLS L2VPN Graceful Restart feature enables a switch configured with the Label Distribution Protocol (LDP) Graceful Restart (GR) to assist its neighboring switches to recover gracefully from an interruption in service. The neighboring switches must be configured with Multiprotocol Label Switching (MPLS) LDP Stateful Switchover/Nonstop Forwarding (SSO/NSF) Support and Graceful Restart (GR). The MPLS LDP GR functions in helper mode, which means that it can only help recover switches that are enabled with MPLS SSO/NSF and GR. If the switch with the LDP GR fails, its peer switches cannot help it recover.

When you enable MPLS LDP GR on a switch that peers with an MPLS LDP SSO/NSF-enabled switch, the SSO/NSF-enabled switch can maintain its forwarding state when the LDP session between them is interrupted. While the SSO/NSF-enabled switch recovers, the peer switch forwards packets using stale information. This process enables the SSO/NSF-enabled switch to become operational more quickly.

Label Distribution Protocol Graceful Restart

Label Distribution Protocol Graceful Restart (LDP GR) works in Strict Helper mode, where it helps a neighboring switch configured with MPLS LDP Stateful Switchover/Nonstop Forwarding (SSO/NSF) to recover from disruption in service without losing its MPLS forwarding state.

In a typical scenario, three switches and LDP sessions are established between the first switch (Switch 1) and the second switch (Switch 2), as well as between Switch 2 and the third switch (Switch 3). Switch 2 is configured with MPLS LDP SSO/NSF. Switches 1 and 3 are configured with MPLS LDP GR and a label switched path (LSP) is established between Switch 1 and Switch 3.

In this scenario, if there is a disruption of service at Switch 2, Switches 1 and 3 (configured with LDP GR) help Switch 2 (configured with LDP SSO/NSF) to recover from the disruption by performing the following actions:

  • Switch 1 notices an interruption in service with Switch 2. (Switch 3 also performs the same actions in this process.)
  • Switch 1 marks all the label bindings from Switch 2 as stale but continues to use the bindings for MPLS forwarding.
  • Switch 1 reestablishes an LDP session with Switch 2 but keeps its stale label bindings.
  • Both switches readvertise their label binding information. If Switch 1 relearns a label from Switch 2 after the session has been established, the stale flags are removed.

Licensing Requirements for EoMPLS Layer 2 VPN Graceful Restart

The following table shows the licensing requirements for this feature:

 

Product
License Requirement

Cisco DCNM

IP tunnels require a LAN Enterprise license. For a complete explanation of the DCNM licensing scheme and how to obtain and apply licenses, see the Cisco DCNM Installation and Licensing Guide, Release 5.x.

Cisco NX-OS

Layer 2 MVPNs require an MPLS license. For a complete explanation of the Cisco NX-OS licensing scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.

Guidelines and Limitations for EoMPLS Layer 2 VPN Graceful Restart

EoMPLS Layer 2 VPN Graceful Restart has the following configuration guidelines and limitations:

  • Multiprotocol Label Switching (MPLS) Label Distribution Protocol (LDP) Graceful Restart (GR) is supported in Strict Helper mode.
  • Tag Distribution Protocol (TDP) sessions are not supported. Only LDP sessions are supported.
  • MPLS LDP GR cannot be configured on label-controlled ATM (LC-ATM) interfaces.

Configuring EoMPLS Layer 2 VPN Graceful Restart

Repeat this task to configure LDP Graceful Restart on each neighboring NX-OS device.

SUMMARY STEPS

1.blank.gif configure terminal

2.blank.gif mpls ldp configuration

3.blank.gif mpls ldp graceful-restart

4.blank.gif interface type slot / port

5.blank.gif mpls ip

6.blank.gif (Optional) copy running-config start-up config

DETAILED STEPS

 

Command
Purpose

Step 1

configure terminal

 

switch# configure terminal

switch(config)#

Enters global configuration mode.

Step 2

mpls ldp configuration

 

switch(config)# mpls ldp configuration

switch(config-ldp)#

Enters Multiprotocol Label Switching (MPLS) Label Distribution Protocol (LDP) configuration mode.

Step 3

mpls ldp graceful-restart

 

switch(config-ldp)# mpls ldp graceful-restart

Enables the switch to protect the LDP bindings and MPLS forwarding state during a disruption in service.

Step 4

interface t ype slot / port

 

switch(config-ldp)# interface ethernet 2/12

switch(config-if)#

Enters interface configuration mode and configures the specified interface.

Step 5

mpls ip

 

switch(config-if)# mpls ip

Configures MPLS hop-by-hop forwarding on this interface.

Step 6

copy running-config startup-config

 

switch(config-if)# copy running-config startup-config

(Optional) Saves this configuration change.

Verifying the EoMPLS Layer 2 VPN Graceful Restart Configuration

To verify PW and VFI configuration information, perform one of the following tasks:

Command
Purpose

show mpls ldp graceful-restart

Displays Graceful Restart sessions and session parameters.

show mpls ldp neighbor graceful-restart

Displays the Graceful Restart information for the LDP sessions.

show run mpls ldp all

Displays information about all of the running LDP sessions.

Monitoring Tunnel Interfaces

You can configure DCNM to collect tunnel interface statistics. Choose Interfaces > Logical > Tunnel from the Feature Selector and navigate to the interface that you want to collect statistics on.

You see the Port Traffic Statistics window. You can collect statistics on input and output (packet and byte) counters, broadcast, multicast, and unicast traffic.

See the Fundamentals Configuration Guide, Cisco DCNM for LAN, Release 5.x , for more information on collecting statistics for layer 3 interfaces.

Configuration Examples for EoMPLS Layer 2 VPN Graceful Restart

The following example shows how to enable MPLS LDP graceful restart:

feature mpls ldp
interface Ethernet2/12
mpls ip
mpls ldp configuration
no shutdown
no mpls ip default-route
backoff 15 120
logging neighbor-changes
logging password rollover
logging password configuration
no explicit-null
graceful-restart
graceful-restart timers forwarding-holding 120
graceful-restart timers max-recovery 120
graceful-restart timers neighbor-liveness 120
holdtime 180
discovery hello interval 5
discovery hello holdtime 15
discovery targeted-hello interval 10
discovery targeted-hello holdtime 90
no discovery targeted-hello accept
router-id Lo0 force
advertise-labels
label allocate global host-routes
 

Additional References for EoMPLS Layer 2 VPN Graceful Restart

For additional information related to EoMPLS Layer 2 VPN GR, see the following sections:

Related Documents

Related Topic
Document Title

MPLS commands

Cisco Nexus 7000 Series NX-OS MPLS Command Reference

MPLS Label Distribution Protocol

“MPLS LDP Graceful Restart” chapter

MIBs <Optional: remove if not applicable>

MIBs
MIBs Link

MPLS-LDP-STD-MIB

To locate and download MIBs, go to the following URL:

http://www.cisco.com/dc-os/mibs

Feature History for EoMPLS Layer 2 VPN Graceful Restart

Table 28-1 lists the release history for this feature.

 

Table 28-1 Feature History for EoMPLS Layer 2 VPN Graceful Restart
Feature Name
Releases
Feature Information

EoMPLS Layer 2 VPN Graceful Restart

6.2(2)

The EoMPLS Layer 2VPN Graceful Restart feature enables a switch configured with the Label Distribution Protocol (LDP) Graceful Restart (GR) to assist its neighboring switches to recover gracefully from an interruption in service.

IP tunnels in VDC other than default

4.2(1)

This features was introduced.