(Optional) Adjusting C-BSR Control Parameters

Context

Candidate bootstrap routers (C-BSRs) automatically elect a BSR in a PIM domain. Initially, 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 C-BSRs have the same priority, the one with a larger IP address wins. 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 within the PIM domain. The Bootstrap message contains a hash mask which is used for hash calculation in C-RP election.

The BSR periodically sends Bootstrap messages. When the C-BSRs receive the Bootstrap message, they start the holdtime timer. If they do not receive any Bootstrap message from the BSR before the holdtime timer expires, they consider that the BSR has failed and initiate the election of a new BSR. The interval for sending Bootstrap messages must be shorter than the Bootstrap message holdtime.

You can configure the C-BSR priority, the BSR hash mask length, interval for sending Bootstrap messages, and Bootstrap message holdtime on a switch. To prevent BSR spoofing, set a range of valid BSR addresses.

Default Settings

Table 1 lists the default settings of C-BSRs.

**Table 1** Default settings of C-BSRs
Parameter	Default Setting
Interval for sending Bootstrap messages	60s
Holdtime of Bootstrap messages	130s

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

Procedure

Configure parameters contained in a Bootstrap message for a C-BSR.
1. Run system-view
  The system view is displayed.
2. Run pim [ vpn-instance vpn-instance-name | all-instance ]
  The PIM view is displayed.
3. Run c-bsr priority priority
  The priority of the C-BSR is configured.
4. Run c-bsr hash-length priority
  The hash mask length of the C-BSR is configured.
5. Run c-bsr interval interval
  The interval for sending Bootstrap messages is configured.
6. Run c-bsr holdtime interval
  The holdtime of the Bootstrap message received from the BSR is configured.
Configure a valid BSR address range on a PIM device.
1. Run system-view
  The system view is displayed.
2. Run pim [ vpn-instance vpn-instance-name | all-instance ]
  The PIM view is displayed.
3. Run bsr-policy basic-acl-number
  The range of valid BSR addresses is configured.
  
  When configuring an ACL rule for the switch, use the permit parameter to configure the switch to accept only Bootstrap messages with source addresses in a specified range. If no rule is configured in the ACL, the switch discards Bootstrap messages from all source addresses.