Configuring LDP FRR

Pre-configuration Tasks

There are two types of LDP FRR: manual LDP FRR and Auto LDP FRR. Configure LDP FRR by perform either of the following pre-configuration tasks as required.

Before configuring manual LDP FRR, complete the following tasks:
- Configure a local LDP session. For details, see Configuring Basic Functions of MPLS LDP.
- Configure single-hop BFD if BFD-based manual LDP FRR needs to be configured. For details, see BFD Configuration in the S2720, S5700, and S6700 V200R019C10 Configuration Guide - Reliability.
Before configuring Auto LDP FRR, complete the following tasks:
- Configure a local LDP session. For details, see Configuring Basic Functions of MPLS LDP.
- Configure IS-IS Auto FRR or OSPF IP FRR. For details about IS-IS Auto FRR, see Enabling IPv4 IS-IS Auto FRR under IPv4 IS-IS Configuration in the S2720, S5700, and S6700 V200R019C10 CLI-based Configuration - IP Unicast Routing Configuration Guide. For details about OSPF IP FRR, see Configuring OSPF IP FRR under OSPF Configuration in the S2720, S5700, and S6700 V200R019C10 CLI-based Configuration - IP Unicast Routing Configuration Guide.

To implement millisecond-level switching, perform Configuring Static BFD to Detect an LDP LSP or Configuring Dynamic BFD for LDP LSPs.

Context

LDP FRR is classified into the following types:

Manual LDP FRR: A backup LSP is configured manually by specifying an outbound interface or a next hop. The configuration is complex and flexible. Manual LDP FRR applies to simple networks.
Auto LDP FRR: A backup LSP is automatically created based on a specified policy. The configuration is simple and prevents loops. Auto LDP FRR applies to complex and large networks.

Select a type according to situations on your network.

Perform the following steps on the ingress or transit node.

Procedure

Configuring manual LDP FRR
1. Run system-view
  The system view is displayed.
2. Run interface interface-type interface-number
  The interface view is displayed.
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
  
  Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
4. Run mpls ldp frr nexthop nexthop-address [ ip-prefix ip-prefix-name ] [ priority priority ]
  LDP FRR is enabled on the interface.
  
  By default, no interface is enabled with LDP FRR.
  
  On the same interface, you can configure up to 10 LDP FRR entries with different precedences. According to different precedences, only one bypass LSP is generated. The smaller the value is, the higher the precedence is. By default, the precedence value is 50.
  LDP FRR cannot be enabled or disabled during the LDP GR.
  
  If manual LDP FRR and IP FRR are deployed concurrently, IP FRR is used preferentially.
  
  When the undo mpls ldp command is run to disable the LDP function in the system view or the undo mpls ldp command is run to disable the LDP function in the interface view, the LDP FRR configuration in the interface view is not automatically deleted. Only the LDP FRR function is invalid.
  
  In manual LDP FRR configuration, the backup LSP must be in liberal state. That is, the route state of the bypass LSP from Ingress to Egress node must be "Inactive Adv".
5. (Optional) Configuring a Static BFD Session to Report Faults of the Detected Service Module:
  The procedure is only applicable to configure the LDP FRR based on static BFD.
  1. Run quit
    
    Return to the system view.
  2. Run bfd session-name
    
    The created BFD session view is displayed.
  3. Run process-pst
    
    The BFD session is enabled to report faults of the associated LDP LSP to the system.
    
    By default, a static BFD session cannot report faults of the monitored service module to the system.
  4. Run commit
    
    The configuration is committed.
Configuring Auto LDP FRR
1. Run system-view
  The system view is displayed.
2. Run mpls ldp
  The MPLS-LDP view is displayed.
3. Run auto-frr lsp-trigger { all | host | ip-prefix ip-prefix-name | none }
  A policy for triggering backup LDP LSP establishment is configured.
  
  By default, LDP uses backup routes to addresses with 32-bit masks to set up backup LSPs.
  - During the LDP GR process, a policy for triggering the backup LDP LSP establishment cannot be changed.
  - Auto LDP FRR depends on IGP auto FRR. After the frr (IS-IS) or frr (OSPF) command is used to enable IGP auto FRR, Auto LDP FRR will be automatically enabled. The auto-frr lsp-trigger command is used to configure or change a policy for triggering backup LDP LSP establishment.
  - If both the auto-frr lsp-trigger command and the lsp-trigger command are run, the established backup LSPs satisfy both the policy for triggering LDP LSP establishment and the policy for triggering backup LDP LSP establishment.

Verifying the Configuration

Run the display mpls lsp command to check information about LSPs enabled with LDP FRR.
Run the display bfd interface [ interface-type interface-number ] command to check information about the BFD interface.