Configuring Auto LDP FRR
By configuring Auto LDP FRR, you can quickly switch traffic to the backup LSP when a link fails, which ensures uninterrupted traffic transmission.
Pre-configuration Tasks
Before configuring Auto LDP FRR, complete the following tasks:
Configure a local LDP session. For details, see Configuring Basic Functions of MPLS LDP.
Configure Auto IGP FRR. For details, see CloudEngine 12800 and 12800E Series Switches Configuration Guide - IP Routing.
Context
After IGP auto FRR is enabled using the frr command, auto LDP FRR is automatically enabled. If you need to adjust the backup LDP LSP establishment policy, configure auto LDP FRR on the ingress or transit node.
On a network with ECMP enabled, if the same type of devices reside on both ends of ECMP links and an optical fiber between the two devices is disconnected, network-wide protection fails to take effect because backup path calculation is not supported on such a network. To resolve this issue, enable the coexistence of ECMP and FRR so that protection paths can be established for the ECMPs.
Procedure
- Configuring Auto LDP FRR
- 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.
The auto-frr lsp-trigger command takes effect in either the MPLS LDP view or MPLS-LDP-IPv4 view. If the command is configured in both views, only the latest configuration takes effect.
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.
- (Optional) Configuring LDP Graceful Deletion
If the primary link goes Down and the LDP session on the primary link goes Down accordingly, LDP immediately instructs the upstream device to withdraw labels and triggers LDP FRR, and the LSP convergence on the secondary link requires LDP to allocate labels to the upstream device again, prolonging the convergence time and traffic switching using FRR. As a result, packet loss occurs.
If LDP graceful deletion is configured and the LDP session goes Down, LDP delays the LDP session deletion and reserves the relevant labels and LSP. The LSP on the secondary link does not require LDP to allocate labels to the upstream device again, shortening traffic switching using LDP FRR and reducing packet loss.
Run graceful-delete
LDP graceful deletion is enabled.
By default, LDP graceful deletion is disabled.
Run graceful-delete timer time
The value of the graceful deletion timer is set.
By default, the value of the graceful deletion timer is 5 seconds.
After the LDP session goes Down, forwarding entries on the LSR remain unchanged for the time specified by the graceful deletion timer.
If the value of the graceful deletion timer is too large, the invalid LSPs will be kept for a long time, consuming system resources.
- Run auto-frr lsp-trigger { all | host | ip-prefix ip-prefix-name | none }
- Enabling the Coexistence of ECMP and FRR
This function is supported only when the card interoperability mode of the device is enhanced mode.
