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Configuring IP Multicast Routing
Configuring PIM Version 2
IPC-418
Cisco IOS IP Configuration Guide
The Cisco PIM Version 2 implementation allows interoperability and transition between Version 1 and
Version 2, although there might be some minor problems. You can upgrade to PIM Version 2
incrementally. PIM Versions 1 and 2 can be configured on different routers within one network.
Internally, all routers on a shared media network must run the same PIM version. Therefore, if a PIM
Version 2 router detects a PIM Version 1 router, the Version 2 router downgrades itself to Version 1 until
all Version 1 routers have been shut down or upgraded.
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 accomplished by Auto-RP, but the BSR is part of the PIM
Version 2 specification.
To avoid a single point of failure, you can configure several candidate BSRs in a PIM domain. A BSR is
elected among the candidate BSRs automatically; they use bootstrap messages to discover which BSR
has the highest priority. This router then announces to all PIM routers in the PIM domain that it is the
BSR.
Routers that are configured as candidate RPs then unicast to the BSR the group range for which they are
responsible. The BSR includes this information in its bootstrap messages and disseminates it to all PIM
routers in the domain. Based on this information, all routers will be able to map multicast groups to
specific RPs. As long as a router is receiving the bootstrap message, it has a current RP map.
Prerequisites
• When PIM Version 2 routers interoperate with PIM Version 1 routers, Auto-RP should have already
been deployed.
• Because bootstrap messages are sent hop by hop, a PIM Version1 router will prevent these messages
from reaching all routers in your network. Therefore, if your network has a PIM Version 1 router in
it, and only Cisco routers, it is best to use Auto-RP rather than the bootstrap mechanism.
PIM Version 2 Configuration Task List
There are two approaches to using PIM Version 2. You can use Version 2 exclusively in your network,
or migrate to Version 2 by employing a mixed PIM version environment. When deploying PIM Version 2
in your network, use the following guidelines:
• If your network is all Cisco routers, you may use either Auto-RP or the bootstrap mechanism (BSR).
Note The simultaneous deployment of Auto-RP and BSR is not supported.
• If you have routers other than Cisco in your network, you need to use the bootstrap mechanism.
To configure PIM Version 2, perform the tasks described in the following sections. The tasks in the first
section are required; the tasks in the remaining sections are optional.
• Specifying the PIM Version (Required)
• Configuring PIM Version 2 Only (Optional)
• Making the Transition to PIM Version 2 (Optional)
• Monitoring the RP Mapping Information (Optional)