Cisco Systems 78-11741-02 Making the Transition to PIM Version, Deciding When to Configure a BSR

Configuring IP Multicast Routing

Configuring PIM Version 2

Note The Cisco IOS implementation of PIM BSR uses the value 0 as the default priority for candidate RPs and BSRs. This implementation predates the draft-ietf-pim-sm-bsr IETF draft, the first IETF draft to specify 192 as the default priority value. The Cisco IOS implementation, thus, deviates from the IETF draft. To comply with the default priority value specified in the draft, you must explicitly set the priority value to 192.

Consider the following scenarios when deciding which routers should be RPs:

•In a network of Cisco routers where only Auto-RP is used, any router can be configured as an RP.

•In a network of routers that includes only Cisco PIM Version 2 routers and routers from other vendors, any router can be used as an RP.

•In a network of Cisco PIM Version 1 routers, Cisco PIM Version 2 routers, and routers from other vendors, only Cisco PIM Version 2 routers should be configured as RPs.

To configure a router to be a candidate RP, use the following command in global configuration mode:

Command	Purpose
Router(config)# ip pim rp-candidate type number	Configures the router to be a candidate RP.
[group-list access-list] [priority value]

For examples of configuring PIM Version 2, see the section “PIM Version 2 Examples” later in this chapter.

Note The Cisco IOS implementation of PIM BSR selects an RP from a set of candidate RPs using a method that is incompatible with the specification in RFC 2362. Refer to CSCdy56806 using the Cisco Bug Toolkit for more information. See the “RFC 2362 Interoperable Candidate RP Example” section on page 450 for a configuration workaround.

Making the Transition to PIM Version 2

On each LAN, the Cisco implementation of PIM Version 2 automatically enforces the rule that all PIM messages on a shared LAN are in the same PIM version. To accommodate that rule, if a PIM Version 2 router detects a PIM Version 1 router on the same interface, the Version 2 router downgrades itself to Version 1 until all Version 1 routers have been shut down or upgraded.

Deciding When to Configure a BSR

If there are only Cisco routers in your network (no routers from other vendors), there is no need to configure a BSR. Configure Auto-RP in the mixed PIM Version 1/Version 2 environment.

Note The simultaneous deployment of Auto-RP and BSR is not supported.

Cisco IOS IP Configuration Guide

IPC-421