Adjusting Forwarding Parameters

Parameters associated with PIM forwarding include the interval for sending Join/Prune messages, holdtime carried by a Join/Prune message, policy for filtering Join/Prune messages, and lan-delay and override-interval carried by a Hello message.

Context

Join messages indicate that a multicast router requires upstream devices to forward multicast data, and Prune messages indicate that a multicast router requires upstream devices to stop forwarding multicast data.

After the first member joins a multicast group, the router sends a Join message through the upstream interface to require the upstream router to forward multicast packets to this network segment.

On a PIM-SM network, the router periodically sends Join messages to prevent rendezvous point tree (RPT) branches from being pruned off due to timeout.
After the last member of a group leaves, the router sends a Prune message through the upstream interface to request the upstream router to perform the prune action. If other downstream routers exist on this network segment, they must send the Join message to override the prune action.

A Hello message carries the lan-delay and override-interval attributes.
- lan-delay specifies the delay in transmitting Prune messages on a shared network segment.
- override-interval specifies the period allowed for overriding the prune action. If the routers still need to receive the multicast data, they must send Join messages upstream within the override-interval.
The Prune-Pending Timer (PPT) indicates the period between the time the router receives a Prune message from the downstream interface and the time the prune action is performed. If the downstream interface receives a Join message within the PPT, the prune action is cancelled.

You can set forwarding parameters either globally or on an interface.

Global configuration: takes effect on all interfaces.
Interface-specific configuration: takes precedence over the global configuration. If an interface-specific configuration is not available, the interface uses the global configuration.

Procedure

Set forwarding parameters globally.
1. Run system-view
  The system view is displayed.
2. Run pim [ vpn-instance vpn-instance-name ]
  The PIM view is displayed.
3. Run timer join-prune interval
  An interval is set for all interfaces on the router to send Join/Prune messages.
4. Run holdtime join-prune interval
  The holdtime is set for Join/Prune messages to be sent by all interfaces on the router.
  
  An upstream router determines the period for a downstream interface to hold the join or prune state based on the holdtime carried in the Join/Prune message received from the downstream interface.
5. Run hello-option lan-delay interval
  The lan-delay is set for Hello messages to be sent by all interfaces on the router.
  
  If router interfaces on a shared network segment have different lan-delay values, the maximum lan-delay value is used by negotiation.
6. Run hello-option override-interval interval
  The override-interval is set for Hello messages to be sent by all interfaces on the router.
  
  If router interfaces on a shared network segment have different override-intervals, the maximum override-interval is used by negotiation.
7. Run neighbor-check { receive | send }
  The neighbor check function is configured.
  
  You can specify receive and send to enable the PIM neighbor check function for both received and sent Join/Prune and Assert messages.
8. Run commit
  The configuration is committed.
Set forwarding parameters for a specific interface.
1. Run system-view
  The system view is displayed.
2. Configure a basic or an advanced ACL as needed.
  - Configure a basic ACL.
    1. Run acl [ number ] basic-acl-number [ match-order { auto | config } ]
      A basic ACL is created, and the basic ACL view is displayed.
    2. Run rule [ rule-id ] [ name rule-name ] { deny | permit } source { source-ip-address { source-wildcard | 0 } | any }
      Rules are configured for the basic ACL.
  - Configure an advanced ACL.
    1. Run acl { name advance-acl-name [ advance | [ advance ] number advance-acl-number ] | [ number ] advance-acl-number } [ match-order { config | auto } ]
      
      An advanced ACL is created, and the advanced ACL view is displayed.
    2. Run rule [ rule-id ] [ name rule-name ] { deny | permit } ip [ destination { destination-ip-address { destination-wildcard | 0 } | any } | source { source-ip-address { source-wildcard | 0 } | any } ] ^*
      
      Rules are configured for the advanced ACL.
3. Run quit
  Return to the system view.
4. Run interface interface-type interface-number
  The PIM interface view is displayed.
5. Run pim timer join-prune interval
  An interval is set for the interface to send Join/Prune messages.
6. Run pim holdtime join-prune interval
  The holdtime is set for Join/Prune messages to be sent by the interface.
7. Run pim hello-option lan-delay interval
  The lan-delay is set for Hello messages to be sent by the interface.
8. Run pim hello-option override-interval interval
  The override-interval is set for Hello messages to be sent by the interface.
9. Run pim join-policy { { advanced-acl-number | acl-name acl-name } | asm { basic-acl-number | acl-name acl-name } | ssm { advanced-acl-number | acl-name acl-name } }
  A policy is created for filtering join information in Join/Prune messages.
  
  The router filters join information in Join/Prune messages based on source addresses or both source and group addresses.
  
  If asm is specified, run the rule command in the basic ACL view and set the source parameter to the multicast group address range of join information.
  
  If ssm is specified, run the rule command in the advanced ACL view, set the source parameter to the multicast source address range of join information, and set the destination parameter to the multicast group address range of join information.
  - If a Join message's join information matches an ACL rule and the action is permit, the device permits this message.
  - If a Join message's join information matches an ACL rule and the action is deny, the device denies this message.
  - If a Join message's join information does not match any ACL rule, the device denies this message.
  - If a specified ACL does not exist or does not contain rules, the device denies all Join messages that contain join information.
10. Run commit
  The configuration is committed.