BSR uses 224.0.0.13 for BSR announcements (from BSR to all pim routers) and unicast for RP announcements (from RP to BSR router).
Auto-RP uses 224.0.1.39 for RP announcements (from RP to MA) and 224.0.1.40 for MA announcements (from MA to all pim routers).
On hub-n-spoke networks, when auto-rp announcements must pass between the spokes, you cannot use "ip nbma-mode", because this works only in sparse mode (and announcements are in dense). You have to use BSR or create a pim-enabled tunnel between the spokes.
BSR uses only sparse-mode. When using BSR & "sparse-dense-mode", you might need to add "no ip pim dm-fallback" to prevent groups without an RP from operating in dense mode.
Auto-RP uses dense-mode for its own announcements, so you have to use one of the following on each pim enabled router:
1) "sparse-dense-mode"
2) "sparse-mode" & "ip pim auto-rp listener"
In BSR we cannot define neither the interval of BSR announcements, nor the scope of them (we can define the RP announcements). In Auto-RP we can define all of them.
In Auto-RP we cannot define the priority of each RP. The RP with the higher ip address wins. In BSR we can define the priority of each RP.
To filter BSR announcements from entering/leaving your network, you can use "ip pim bsr-border".
To filter Auto-RP announcements entering/leaving your network, you can use "ip multicast boundary ACL in/out filter-autorp".
Friday, January 11, 2008
How to choose between Auto-RP and BSR
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Thanks, this is the best set of collected points i've seen!
ReplyDeleteAsh
I always prefer BSR instead of auto RP. Main reason for selection is that it is not restricted to cisco domain :).
ReplyDeleteregards
shivlu jain
good summarized post.
ReplyDeleteReally great post. Thx
ReplyDeletethx was struggling to find a plain comparison of these two excellend post
ReplyDeletethanks
eoghan
One more point to note here: As BSR was written as part of the PIM version 2 specification and meant to be an open dynamical RP selection protocol, it supports PIM v2, whereas AutoRP technically does not.
ReplyDeleteCisco Documentation wording:
BSR Election and Functionality
PIM uses the BSR to discover and announce RP-set information for each group prefix to all the routers in a PIM domain. This is the same function performed by Auto-RP, but the BSR is part of the PIM Version 2 specification. The BSR mechanism interoperates with Auto-RP on Cisco routers.
Cisco Documentation Link:
http://www.cisco.com/en/US/docs/ios-xml/ios/ipmulti_pim/configuration/12-4t/imc_basic_cfg.html#GUID-D1656247-AFA8-4F67-8114-FB290E579FDD