Setup Guide

Electing an RP using the BSR Mechanism
Every PIM router within a domain must map a particular multicast group address to the same RP. The group-to-RP mapping
may be statically or dynamically configured. RFC 5059 specifies a dynamic, self-configuring method called the Bootstrap Router
(BSR) mechanism, by which an RP is elected from a pool of RP candidates (C-RPs).
Some routers within the domain are configured to be C-RPs. Other routers are configured to be Bootstrap Router candidates
(C-BSRs); one router is elected the BSR for the domain and the BSR is responsible for forwarding BSM containing RP-set
information to other routers.
The RP election process is as follows:
1. C-BSRs flood their candidacy throughout the domain in a BSM. Each message contains a BSR priority value, and the C-BSR
with the highest priority value becomes the BSR.
2. Each C-RP unicasts periodic Candidate-RP-Advertisements to the BSR. Each message contains an RP priority value and the
group ranges for which it is a C-RP.
3. The BSR collects the most efficient group-to-RP mappings and periodically updates it to all PIM routes in the network.
4. The BSR floods the RP-Set throughout the domain periodically in case new C-RPs are announced, or an RP failure occurs.
Constraints
1. When a multicast group range is removed from the ACL group list, the E-BSR sends the advertisements to the group with
hold-time as 0 only when the C-RP timer expires. Till the timer expires, the C-RP will act as a RP for that multicast group.
2. In E-BSR, if the C-RP advertisements are not in synchronization with the standby, first few BCM C-RP advertisement might
not have the complete list of RP mappings. Due to this, there is a possibility of RP mapping timeout and momentary traffic
loss in the network.
3. If you configure a secondary VLT peer as an E-BSR and in case of ICL flap or failover, the VLT lag will be down resulting a
BSM timeout in the PIM domain and a new BSR will be elected. Hence, it is recommended to configure the primary VLT peer
as E-BSR.
To enable BSR election for IPv4 or IPv6, perform the following steps:
1. Enter the following IPv4 or IPv6 command to make a PIM router a BSR candidate:
CONFIGURATION
ip pim bsr-candidate
ipv6 pim bsr-candidate
2. Enter the following IPv4 or IPv6 command to make a PIM router a RP candidate:
CONFIGURATION
ip pim rp-candidate
ipv6 pim rp-candidate
3. Display IPv4 or IPv6 Bootstrap Router information.
EXEC Privilege
show ip pim bsr-router
Example:
DellEMC# show ip pim bsr-router
PIMv2 Bootstrap information
This system is the Bootstrap Router (v2)
BSR address: 7.7.7.7 (?)
BSR Priority: 0, Hash mask length: 30
Next bootstrap message in 00:00:08
This system is a candidate BSR
Candidate BSR address: 7.7.7.7, priority: 0, hash mask length: 30
DellEMC#
show ipv6 pim bsr-router
Example:
DellEMC#show ipv6 pim bsr-router
PIMv2 Bootstrap information
BSR address: 200::1 (?)
PIM Sparse-Mode (PIM-SM)
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