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 IPv6 multicast data, and Prune messages indicate that a multicast router requires upstream devices to stop forwarding IPv6 multicast data.

After the first member joins a multicast group, the router sends a Join message to request its upstream router to forward required IPv6 multicast data.

On an IPv6 PIM-SM network, the router periodically sends Join messages to prevent RPT branches from being pruned off due to timeout.
After the last member of a group leaves, the router sends a Prune message to request its upstream router to perform the prune action. If other downstream routers still need to receive multicast data for the group, they must send Join messages to the upstream router within the set override-interval 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 interval for overriding the prune action.
The relationship between lan-delay, override-interval, and PPT is: lan-delay + override-interval = PPT. The Prune-Pending Timer (PPT) indicates the period from the time when the router receives a Prune message from a downstream interface to the time when the router performs the prune action. If the router receives a Join message from the downstream interface within the PPT, the router does not perform the prune action.

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.

To enhance the security of IPv6 PIM forwarding, configure a source address- and group address-based policy for filtering Join/Prune messages on an interface.

Procedure

Set forwarding parameters globally.
1. Run system-view
  The system view is displayed.
2. Run pim-ipv6
  The IPv6 PIM view is displayed.
3. Run timer join-prune interval
  The interval for the interfaces of the router to send Join/Prune messages is set.
4. Run holdtime join-prune interval
  The value of the holdtime field carried by a sent Join/Prune message is set.
  
  After receiving a Join/Prune message from a downstream interface, an upstream router determines the period for keeping the join or prune state of the downstream interface based on the value of the holdtime field in the Join/Prune message.
  
  The value of the holdtime field carried by a Join/Prune message must be 3.5 times of the interval for sending Join/Prune messages.
5. Run hello-option lan-delay interval
  The value of the lan-delay field carried by a sent Hello message is set.
  
  When the values of lan-delay fields carried by Hello messages sent by the interfaces on a shared network segment are different, the largest one of these values is used.
6. Run hello-option override-interval interval
  The value of the override-interval field carried by a sent Hello message is set.
  
  When the values of override-interval fields carried by Hello messages sent by the interfaces on a shared network segment are different, the maximum one of these values is used.
7. Run neighbor-check { receive | send }
  The neighbor check function is configured.
  
  You can specify both receive and send to enable the IPv6 PIM neighbor check function for both the received and sent Join/Prune messages 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 ACL6 as needed.
  - Configure a basic ACL6.
    1. Run acl ipv6 [ number ] basic-acl6-number [ match-order { auto | config } ]
      A basic ACL6 is created, and the basic ACL6 view is displayed.
    2. Run rule [ rule-id ] [ name rule-name ] { deny | permit } [ fragment | source { source-ipv6-address prefix-length | source-ipv6-address/prefix-length | any } ] ^*
      Rules are configured for the basic ACL6.
  - Configure an advanced ACL6.
    1. Run acl ipv6 { name advance-acl6-name [ advance | [ advance ] number advance-acl6-number ] | [ number ] advance-acl6-number } [ match-order { config | auto } ]
      
      An advanced ACL6 is created, and the advanced ACL6 view is displayed.
    2. Run rule [ rule-id ] [ name rule-name ] { deny | permit } ipv6 [ destination { destination-ipv6-address prefix-length | destination-ipv6-address/prefix-length | any } | source { source-ipv6-address prefix-length | source-ipv6-address/prefix-length | any } ] ^*
      
      Rules are configured for the advanced ACL6.
3. Run quit
  Return to the system view.
4. Run interface interface-type interface-number
  The IPv6 PIM interface view is displayed.
5. Run pim ipv6 timer join-prune interval
  The interval at which the interface sends Join/Prune messages is set.
6. Run pim ipv6 holdtime join-prune interval
  The value of the holdtime field carried by a Join/Prune message sent by the interface is set.
7. Run pim ipv6 hello-option lan-delay interval
  The value of the lan-delay field carried by a Hello message sent by the interface is set.
8. Run pim ipv6 hello-option override-interval interval
  The value of the override-interval field carried by a Hello message sent by the interface is set.
9. Run pim ipv6 join-policy { { advanced-acl6-number | acl6-name acl6-name } | asm { basic-acl6-number | acl6-name acl6-name } | ssm { advanced-acl6-number | acl6-name acl6-name } }
  A policy for filtering Join messages contained in Join/Prune messages is configured.
  
  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.