ISID policies are an optional aspect of SPBM which allow additional control of ISIDs for I-VPLS. PBB services using SPBM automatically populate multicast for I-VPLS and static-isids. Incorrect use of isid-policy can create black holes or additional flooding of multicast.
To enable more flexible multicast, ISID policies control the amount of MFIB space used by ISIDs by trading off the default Multicast tree and the per ISID multicast tree. Occasionally customers want services that use I-VPLS that have multiple sites but use primarily unicast. The ISID policy can be used on any node where an I-VPLS is defined or static ISIDs are defined.
The typical use is to suppress the installation of the ISID in the MFIB using use-def-mcast and the distribution of the ISID in SPBM by using no advertise-local.
The use-def-mcast policy instructs SPBM to use the default B-VPLS multicast forwarding for the ISID range. The ISID multicast frame remains unchanged by the policy (the standard format with the PBB OUI and the ISID as the multicast destination address) but no MFIB entry is allocated. This causes the forwarding to use the default BVID multicast tree which is not pruned. When this policy is in place it only governs the forwarding locally on the current B-VPLS.
The advertise local policy ISID policies are applied to both static ISIDs and I-VPLS ISIDs. The policies define whether the ISIDs are advertised in SPBM and whether the use the local MFIB. When ISIDs are advertised they use the MFIB in the remote nodes. Locally the use of the MFIB is controlled by the use-def-mcast policy.
The types of interfaces are summarized in Table: SPBM ISID policies table.
| Service type | ISID policy on B-VPLS | Notes |
|---|---|---|
Epipe |
No effect |
PBB Epipe ISIDs are not advertised or in MFIB. |
I-VPLS |
None: Uses ISID Multicast tree. Advertised ISIDs of I-VPLS. |
I-VPLS uses dedicated (pruned) multicast tree. ISIDs are advertised. |
I-VPLS (for Unicast) |
use-def-mcast no advertise-local |
I-VPLS uses default Multicast. Policy only required where ISIDs are defined. ISIDs not advertised. must be consistently defined on all nodes with same ISIDs. |
I-VPLS (for Unicast) |
use-def-mcast advertise-local |
I-VPLS uses default Multicast. Policy only required where ISIDs are defined. ISIDs advertised and pruned tree used elsewhere. May be inconsistent for an ISID. |
Static ISIDs for I-VPLS interworking |
None: (recommended) Uses ISID Multicast tree |
I-VPLS uses dedicated (pruned) multicast tree. ISIDs are advertised. |
Static ISIDs for I-VPLS interworking (defined locally) |
use-def-mcast |
I-VPLS uses default Multicast. Policy only required where ISIDs are configured or where I-VPLS is located. |
No MFIB for any ISIDs Policy defined on all nodes |
use-def-mcast no advertise-local |
Each B-VPLS with the policy does not install MFIB. Policy defined on all switches ISIDs are defined. ISIDs advertised and pruned tree used elsewhere. May be inconsistent for an ISID. |