Default IBCP session

The BNG UPF always enables the IPoE and PPPoE BBF function features. A compatible BNG CPF uses this as an indication to set up a default IBCP tunnel to send control plane packets, such as DHCP discover or PADI, that do not match an existing session. The default tunnel is signaled as a special PFCP session without a PDN type. The special PFCP session can apply traffic-matching rules the same as any other PFCP session for which the BNG UPF applies rules.

Packets sent over the default In-band Control Plane (IBCP) tunnel include local BNG UPF parameters that are inserted in a network service header. The network service header is inserted between the GTP-U header and the encapsulated control packet. These parameters include the following:

MAC address

This is the MAC address that is associated with the capture SAP on which the IBCP packet was received. The BNG CPF uses the MAC address as a source MAC address when sending control packet responses. In case of inter-UPF resiliency, the BNG CPF can ignore this MAC address and use the FSG MAC address instead. For more information about inter-UPF resiliency, see BNG UPF resiliency.
Layer 2 access ID

The Layer 2 access ID (also known as the logical port) identifies the local port, the LAG, or the pw-port that is used by the capture SAP. The BNG CPF reflects this parameter as is when setting up a session so the BNG UPF installs the session in this context. To simplify provisioning on the BNG CPF, you can provide an alias for the L2 access ID. The alias must be unique within the BNG UPF and cannot overlap with any identifier such as a port or a LAG name.

To configure the L2 access ID alias, use the configure service vpls capture-sap pfcp l2-access-id-alias command.

See IBCP for more information about IBCP.