HLE is an essential Layer 2 bridge service. The data plane consists of a per- subscriber BD that contains the following tables:
MAC table
This table includes the learned MAC address by access and network connections.
flood table
This table includes flood destinations for broadcast, unknown unicast, multicast (BUM) traffic and typically contains access, and network connections.
IPv4 ARP table
This table includes learned ARP entries by access and network connections.
IPv6 neighbor table
This table includes learned neighbor entries by access and network connections.
The ARP and neighbor tables are populated when Assistive Address Resolution (AAR) is enabled.
When MAT is disabled, the ISA forwards packets based on the destination MAC address by performing a lookup in the MAC table and floods BUM traffic to destinations in the flood table.
For flooding traffic, the system does not send a to-be-flooded packet back to where it was received. If the packet is received from one remote network connection, the system does not forward it to another remote network connection.