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 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:
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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. 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
DETAILED STEPS
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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:
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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:
logging password rollover
logging password configuration
graceful-restart timers forwarding-holding 120
graceful-restart timers max-recovery 120
graceful-restart timers neighbor-liveness 120
discovery hello interval 5
discovery hello holdtime 15
discovery targeted-hello interval 10
discovery targeted-hello holdtime 90
no discovery targeted-hello accept
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
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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>
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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
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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. |