H3C Technologies H3C S7500E Series Switches - Manual (Page 145)

6-8
z An RP can serve multiple multicast groups or all multicast groups. Only one RP can serve a
given multicast group at a time.
z A device can serve as a C-RP and a C-BSR at the same time.
As shown in Figure 6-4 , each C-RP periodically unicasts its advertisement messages
(C-RP-Adv messages) to the BSR. A C-RP-Adv message contains the address of the
advertising C-RP and the multicast group range it serves. The BSR collects these
advertisement messages and chooses the appropriate C-RP information for each multicast
group to form an RP-set, which is a database of mappings between multicast groups and RPs.
The BSR then encapsulates the RP-set in the bootstrap messages (BSMs) it periodically
originates and floods the bootstrap messages to the entire PIM-SM domain.
Figure 6-4 BSR and C-RPs
Based on the information in the RP-sets, all routers in the network can calculate the location of
the corresponding RPs based on the following rules:
The C-RP with the highest priority wins.
1) If all the C-RPs have the same priority, their hash values are calculated through the
hashing algorithm. The C-RP with the largest hash value wins.
2) If all the C-RPs have the same priority and hash value, the C-RP with the highest IP
address wins.
The hashing algorithm used for RP calculation is: Value (G, M, C
i
) = (1103515245 *
( (1103515245 * (G & M) + 12345) XOR C
i
) + 12345) mod 2
31
. The table below gives the
meanings of the values in this algorithm.
Table 6-1 Values in the hashing algorithm
Value Description
Value Hash value