When you configure CFM, be aware of the following configuration considerations.
A single switch has a limit of one MEP and one MIP on a C-VLAN or B-VLAN.
The maintenance level for MEPs and MIPs on a given B-VID (in a network) must be configured to the same level for them to respond to a given CFM command.
You can configure global CFM at only one MD level for each switch for each VLAN type.
All nodal MEPs and MIPs are restricted to SPBM B-VIDs.
SMLT Virtual MAC for C-VLAN does not exist, so the switch does not support this option for the l2 ping and l2 traceroute commands.
Autogenerated MEPs are not unique across the entire network unless you configure the global MEP ID on each switch to a different value. You must configure a unique MEP ID at a global level, for CFM.
A single switch can have only one autogenerated MEP or MIP for each B-VLAN or C-VLAN.
Previous explicit CFM configurations of MDs, MAs and MEPs on SPBM B-VLANs continue to be supported. However, if you want to enable autogenerated CFM you must first remove the existing MEP and MIP on the SPBM B-VLAN.
You can assign maintenance levels for each CFM SPBM MEP and MIP to each SPBM B-VLAN individually or you can assign maintenance levels and global MEPs for all SPBM VLANs by following the appropriate procedure:
Important
Only VSP 4450 Series supports CFM configuration on C-VLANs.
CFM breaks the network into sections, called MEPs, so you can determine exactly where the problem exists.
The MEPs and MIPs configured for SPBM VLANs do not respond to CFM messages sent from C-MAC VLANs because the VLAN and packet encapsulation are different.
To forward customer traffic across the core network backbone, SPBM uses IEEE 802.1ah Provider Backbone Bridging (PBB) MAC-in-MAC encapsulation, which hides the customer MAC (C-MAC) addresses in a backbone MAC (B-MAC) address pair. MAC-in-MAC encapsulation defines a B-MAC destination address (BMAC-DA) and a B-MAC source address (BMAC-SA). In SPBM, each node populates its forwarding database (FDB) with the B-MAC information derived from the IS-IS shortest path tree calculations.
Typically the SPBM Backbone Core Bridges (BCBs) in the SPBM cloud only learn the B-MAC addresses. The Backbone Edge Bridges (BEBs) know the Customer MACs on the appropriate BEBs that terminate the virtual services networks (VSNs). As such, the nodes within the SPBM cloud have no knowledge of the C-MAC addresses in the VSNs.
Important
For C-VLANs, you have to trigger an l2 ping to learn the C-MAC address.
For B-VLANs, you do not have to trigger an l2 ping to learn the C-MAC address because IS-IS populates the MAC addresses in the FDB table.
CFM uses either the VLAN MAC or the CFM C-MAC for the BMAC-SA for the C-VLANs. The CFM C-MAC is the value of the management base MAC, which ends in 0x64. The system creates the VLAN MAC after a user adds an IP address to a VLAN.
If a VLAN has a MAC address, the system uses the VLAN MAC as the BMAC-SA by default. If a VLAN does not have a MAC address, the system uses the CFM C-MAC for the BMAC-SA. You may also configure the system to use the CFM C-MAC, even if a VLAN MAC exists.