Brocade Multi-Service IronWare Multicast Configuration Guide (Supporting R05.6.00) - Manual (Page 31)

Multi-Service IronWare Multicast Configuration Guide 19
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IP multicast boundaries
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This feature is useful when the core is running MPLS and multicast routing protocols (like GRE
MVPN). There can be an IGP shortcut path or LSP path which would provide next-hop as the tunnel
interface. The IGPs can route unicast traffic over these tunnels to destinations that are
downstream from the egress router of the tunnel. Without this feature, RPF path through LSP
cannot be directly used to send PIM control packets. With this feature enabled, Multicast control
the packets or traffic would use LSP's underlying native path as RPF Path. If this feature is not
enabled RPF resolution would fail in these scenarios.
Limitations
These are the limitations in determining RPF shortcut.
1. No support for IPv6 multicast
2. No VRF support, only default VRF as MPLS doesn't have VRF support
3. No Support for Static Mroute to LSP tunnel end point
4. No IGP shortcut support for LDP tunnels
5. No support for ECMP between LSP path and non-LSP path
6. No NSR support for shortcut routes as there is no support in RSVP for NSR
7. No IS-IS announce metric feature support
8. No support for recursive BGP shortcut lookup
Enabling RPF shortcut feature
Use this command to enable RPF shortcut for LSP paths. If IGP shortcut was enabled prior to
enabling multicast RPF shortcut, multicast cache entries whose RPF lookup resulted in shortcut
would be marked with PIM_FWD_NEED_REROUTE as there won’t be any PIM neighbor on the MPLS
Interface. If RPF lookup results in the LSP path, then another lookup is done to get the underlying
native route and that route's next-hop is used as the RPF.
Brocade(config)# router pim
Brocade(config-pim-router)# rpf shortcut
After this command is executed, if IGP shortcut is not enabled, then there won't be any LSP paths
to be considered for the RPF lookup. Later, when IGP Shortcut is enabled and LSP path becomes
best path, then change is handled through route change notification.
If there are ECMP LSP paths, ECMP path is chosen based on the multicast ECMP path selection
logic. Enabling this command helps MBGP to accept MPLS tunnel as valid next-hop destination and
to install the route into MRTM.
Use this command, when you disable multicast RPF shortcut feature. It reroutes the multicast
cache entries. RPF for the multicast cache entries return either LSP or non-LSP path depends on
IGP shortcut enabling. This command is only supported for default VRF.
Brocade(config)# router pim
Brocade(config-pim-router)# no rpf shortcut
NOTE
It is recommended to have this multicast RPF shortcut feature enabled when IGP shortcut is
enabled.