Table Of Contents
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:
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 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 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 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) recover from disruption in service without losing its MPLS forwarding state.
In a typical three switch topology scenario, there are 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 it 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
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 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.
1. configure terminal
2. mpls ldp configuration
3. mpls ldp graceful-restart
4. interface type slot/port
5. mpls ip
6. (Optional) copy running-config start-up config
Verifying the EoMPLS Layer 2 VPN Graceful Restart Configuration
To verify PW and VFI configuration information, perform one of the following tasks:
Configuration Examples for EoMPLS Layer 2 VPN Graceful Restart
The following example shows how to enable MPLS LDP graceful restart:feature mpls ldpinterface Ethernet2/12mpls ipmpls ldp configurationno shutdownno mpls ip default-routebackoff 15 120logging neighbor-changeslogging password rolloverlogging password configurationno explicit-nullgraceful-restartgraceful-restart timers forwarding-holding 120graceful-restart timers max-recovery 120graceful-restart timers neighbor-liveness 120holdtime 180discovery hello interval 5discovery hello holdtime 15discovery targeted-hello interval 10discovery targeted-hello holdtime 90no discovery targeted-hello acceptrouter-id Lo0 forceadvertise-labelslabel 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 Topic Document Title
Cisco Nexus 7000 Series NX-OS MPLS Command Reference
MPLS Label Distribution Protocol
"MPLS LDP Graceful Restart" chapter
MIBs MIBs Link
To locate and download MIBs, go to the following URL:
Feature History for EoMPLS Layer 2 VPN Graceful Restart
Table 28-1 lists the release history for this feature.