To support MAC-concentrating network equipment, which translates the original MAC address of a number of subscribers to a single MAC address toward the PPPoE service, the SR OS supports up to 8191 PPPoE sessions per MAC address. Each of these sessions are identified by a unique combination of MAC address and PPPoE session ID.
To set up multiple sessions per MAC, the following limits should be set sufficiently high:
Maximum sessions per MAC in the PPPoE policy
The PPPoE interface session limit in the PPPoE node of the group interface
The PPPoE SAP session limit in the PPPoE node of the group interface
The multiple-subscriber-sap limit in the subscriber management node of the SAP
If host information is retrieved from a local DHCP server, care must be taken that, although a host can be identified by MAC address, circuit ID, remote ID or username, a lease in the DHCP server is, by default, only indexed by MAC address and circuit ID. For example, multiple sessions per MAC address are only supported in this scenario if every host with the same MAC address has a unique Circuit-ID value.
To enable IPv4 address allocation using the internal DCHCPv4 client for multiple PPPoE sessions on a single SAP and having the same MAC address and circuit-ID, the optional CLI parameter allow-same-circuit-id-for-dhcp should be added to the max-sessions-per-mac configuration in the PPP policy. The SR OS local DHCP server detects the additional vendor-specific options inserted by the internal DCHCPv4 client and uses an extended unique key for lease allocation.