(Optional) Setting the Hold-max-cost Timer Value

Context

If an LDP session over the active link fails but an IGP route for the active link is reachable, a node that has LDP-IGP synchronization enabled uses a Hold-max-cost timer to enable an IGP to advertise LSAs or LSPs carrying the maximum route cost, which delays IGP route convergence until an LDP session is established. Therefore, an IGP route for a standby link and an LDP session over the standby link can become available simultaneously.

You can set the Hold-max-cost timer value in either of the following methods:

Setting the Hold-max-cost timer value in the interface view

You can set the Hold-max-cost timer value on a specified interface. This mode applies to the scenario where a few interfaces need to use the Hold-max-cost timer.
Setting the Hold-max-cost timer value in the IGP process

After you set the Hold-max-cost timer value in the IGP process, the Hold-max-cost timers on all interfaces in the IGP process are set to this value. This mode applies to the scenario where many interfaces on a node need to use the Hold-max-cost timer.

A Hold-max-cost timer can be set on either an OSPF or IS-IS interface and can only be set in an IS-IS process, not an OSPF process.

If different Hold-max-cost values on an interface and in an IS-IS process are set, the setting on the interface takes effect.

Select parameters based on networking requirements:

If an IGP carries only LDP services, configure the parameter infinite to ensure that a selected IGP route is kept consistent with the LDP LSP.
If an IGP carries multiple types of services including LDP services, set the value of the parameter value to ensure that a teardown of LDP sessions does not affect IGP route selection or other services.

Procedure

If OSPF is used as an IGP, perform the following steps:
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 ospf timer ldp-sync hold-max-cost { value | infinite }
  The interval for advertising the maximum cost in the LSAs of local LSRs through OSPF is set.
  
  By default, the value of the Hold-max-cost timer is 10 seconds.
If IS-IS is used as an IGP, perform the following steps:
Set the Hold-max-cost timer on a specified IS-IS interface.
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 isis timer ldp-sync hold-max-cost { value | infinite }
  The value of the Hold-max-cost timer is set.
  
  By default, the value of the Hold-max-cost timer is 10 seconds.
Set the Hold-max-cost timer on all IS-IS interfaces in a specified IS-IS process.
1. Run system-view
  The system view is displayed.
2. Run isis [ process-id ]
  The IS-IS process view is displayed.
3. Run timer ldp-sync hold-max-cost { infinite | interval }
  The Hold-max-cost timer is set, which enables IS-IS to keep advertising LSPs carrying the maximum route cost on all interfaces within an IS-IS process.
  
  By default, the value of the Hold-max-cost timer is 10 seconds.