Command Reference Guide

3Com Router 5000 Family and Router 6000 Family crp-policy ● 11
Command Reference
crp-policy
Purpose Use the crp-policy command to restrict the range for valid C-RP and the group
range served by each C-RP, preventing C-RP cheating.
Use the undo crp-policy command to restore the normal state without any
range restriction and regard all the messages received are valid.
Syntax crp-policy acl-number
undo crp-policy
Parameters acl-number
ACL number used by C-RP filter policy. Valid values are
3000 to 3999.
Example Configure C-RP policy on C-BSR router. Only permit 1.1.1.1/32 to act as C-RP which
only serves the group range 225.1.0.0/16.
[3Com-pim] crp-policy 3100
[3Com-pim] quit
[3Com] acl number 3100
[3Com-acl-adv-3100] rule 0 permit ip source 1.1.1.1 0 destination
225.1.0.0 0.0.255.255
View This command can be used in the following views:
■ PIM view
Description This command uses the ACL numbered from 3000 to 3999. The parameter source
in the related rule command indicates C-RP address and destination indicates
the group range the C-RP serves. Upon matching the received C-RP message, only
when the C-RP address in the packet matches source address and the group
address range in the packet is the subset of that in ACL, can this configuration be
regarded successful.
In PIM SM network which uses BSR mechanism, any router can set itself as a C-RP
serving the specific group range. If it is elected in RP election, it will become an RP
serving in the group range.
In BSR mechanism C-RP router unicasts C-RP information to BSR router which is
responsible for advertising all C-RP information to the whole network by using BRP
information.
To prevent C-RP cheating, crp-policy is needed to configure on BSR router to
restrict the range for valid C-RP and the group address range it serves. Each C-BSR
may become a BSR possibly, so the same filter policy should be configured on each
C-BSR.