Configuring IPv6 PIM-SM in the ASM Model

IPv6 PIM-DM and IPv6 PIM-SM cannot be enabled simultaneously on the device.

It is recommended that you enable IPv6 PIM-SM on all interfaces in a PIM-SM domain, so that the interfaces can establish neighbor relationships with all connected PIM devices.

If IPv6 PIM-SM and MLD need to be enabled on the same interface, enable IPv6 PIM-SM, and then enable MLD.

A rendezvous point (RP) can be configured manually or elected from among multiple candidate rendezvous points (C-RPs) based on C-RP information collected and advertised by the bootstrap router (BSR). Manually configuring a static RP reduces bandwidth used for frequent information exchange between the C-RPs and BSR. Dynamically electing an RP based on C-RP information collected and advertised by the BSR simplifies configuration and improves reliability of multicast forwarding because multiple C-RPs are configured.

On an IPv6 PIM-SM network, the embedded RP function is enabled on each device by default. When a device receives a multicast packet sent to a multicast group, it can obtain RP information from the group address. The devices with the embedded RP function do not need to know the mapping between RPs and group addresses beforehand. The range of group addresses that a device can parse can be manually changed.

You can configure a static RP and multiple C-RPs for dynamic RP election. The static RP functions as a backup RP because it has a lower priority. Ensure that all the devices on the network have the same RP information. Inconsistent RP information may cause forwarding failures on the network.

Default Settings

Table 5-10 lists the default settings of the C-BSR and C-RP.

To facilitate PIM-SM domain management, a PIM-SM network is divided into multiple bootstrap router (BSR) administrative domains and a global domain. Each BSR administrative domain maintains only one BSR that serves specified multicast groups. Multicast groups that do not belong to any BSR administrative domain are served by the global domain. A device can join only one administrative domain, so devices in each administrative domain can forward multicast data independently. Data of multicast groups in the global domain can be forwarded through devices in any administrative domain.

Different from IPv4, when configuring the boundary of a BSR administrative domain on an IPv6 network, you can specify the group address range served by the domain and set a scope ID for the domain. On candidate BSRs (C-BSRs), you only need to specify the scope ID of the BSR administrative domain and do not need to specify the group address range served by the BSR administrative domain.

A high volume of multicast data traffic increases the load of an RP and may result in a fault. The DR at the group member side triggers an SPT switchover to reduce the burden of the RP.

By default, a DR at the group member side immediately triggers an SPT switchover after receiving the first multicast data packet. You can configure a traffic rate threshold on a DR at the group member side to trigger an SPT switchover or prevent the DR from triggering an SPT switchover.

Default Settings

Table 5-11 lists the default settings of SPT switchover conditions.

After receiving multicast data from a multicast source, the source DR encapsulates multicast data in a Register message and forwards the message to the RP. Therefore, you can adjust control parameters for source registration on the RP and source DR.

You can perform the following operations on the source DR.

• Configure the register message suppression time. After receiving a Register-Stop message, the source DR stops sending Register messages to the RP during register suppression. The source DR forwards packets again when the register suppression time expires and it receives no more Register-Stop messages.
• Configure the interval at which null Register messages are sent. When the timeout period for keeping the register suppression state is too long or too short, multicast data cannot be forwarded normally. Sending null Register messages during register suppression can relieve this problem.
• Configure the source address for Register messages. The RP cannot receive Register messages from a source DR if the source address of the Register messages is not a unique IPv6 address on the network or if the source address is filtered out by a policy configured on the RP. To enable the RP to receive Register messages from the source DR, configure a new source address for the Register messages.

You can perform the following operations on the RP.

• Configure a policy to filter Register messages. You can specify the source address range of Register messages to improve network security.

Default Settings

Table 5-12 lists the default settings of control parameters for source registration.

When a candidate rendezvous point (C-RP) is configured on the device, the C-RP periodically sends Advertisement messages to a bootstrap router (BSR). The Advertisement messages carry the C-RP priority and the holdtime of Advertisement messages. After receiving Advertisement messages, the BSR starts the C-RP timeout timer. The timer value is set to the holdtime of Advertisement messages. Before the timer expires, the BSR collects the C-RP information in Advertisement messages into an RP-set, encapsulates the RP-set into a Bootstrap message, and advertises the Bootstrap message to all IPv6 PIM devices. If the BSR does not receive any Advertisement message from the C-RP after the timer expires, the BSR considers the C-RP invalid or unreachable on the network. The interval for sending Advertisement messages must be smaller than the holdtime of Advertisement messages so that the BSR can successfully receive the Advertisement messages.

You can manually configure the interval for sending Advertisement messages, C-RP priority and holdtime of Advertisement messages. To prevent C-RP spoofing, set the range of valid C-RP addresses on the BSR. Then the BSR accepts only the Advertisement messages with the source addresses in the specified range.

For the default values of the parameters carried in Advertisement messages, see Configuring an RP.

Candidate bootstrap routers (C-BSRs) automatically elect a BSR in an IPv6 PIM domain. At first, each C-BSR considers itself as a BSR and sends Bootstrap messages to all devices in the domain. When a C-BSR receives a Bootstrap message from another C-BSR, it compares the priority in the received Bootstrap message with its own priority. The C-BSR with a higher priority wins. If the two BSRs have the same priority, the BSR with a larger IP address is preferred. After a C-BSR is elected as the BSR, it encapsulates its own IP address and the RP-Set information into a Bootstrap message and sends the Bootstrap message in the PIM domain. The losers stop sending Bootstrap messages. The Bootstrap message contains a hash mask which is used for hash calculation in rendezvous point (RP) election.

The BSR periodically sends a Bootstrap message to the network. When the other C-BSRs receive the Bootstrap message, they start the holdtime timer. If they do not receive any Bootstrap message from the BSR when the holdtime timer expires, they consider that the BSR fails and initiate the election of a new BSR. The interval for sending Bootstrap messages must be smaller than the holdtime of a Bootstrap message.

You can configure the C-BSR priority, the BSR hash mask length, the interval for sending Bootstrap messages, and the holdtime of Bootstrap messages. To prevent BSR spoofing, set a range of valid BSR addresses on devices, so that the devices receive messages only from the BSRs within the address range.

Default Settings

Table 5-13 lists the default settings of the C-BSR.

For the default values of other C-BSR parameters, see Configuring an RP.

Prerequisites

After configuration of IPv6 PIM-SM in ASM model is complete, you can check information about the BSR, RP, IPv6 PIM interface, IPv6 PIM neighbor, and IPv6 PIM routing table.