User guide

BRIDGE Bridge Functional Description
iMG/RG Software Reference Manual (Switching)
2-38
particular destination might be present. It is also used to create multicast entries and forward multicast packets
to all ports listening for that particular multicast address.
The destination based MAC entries (named also static unicast entries destination based) can be created/deleted
by the user.
For a specific MAC address, there can exist either a static unicast entries source based or a destination unicast
entries source based. However, a destination based MAC entry is updated to be of type static + dynamic if a
packet is received with the source MAC address matching the destination based MAC entry’s MAC address. In
that case, the source port field that was unused for destination based MAC entry type is updated to the source
port on which the MAC address is learnt.
A destination based MAC entry serves the following purpose in packet forwarding:
• For a packet received from a port with its destination MAC address matching a destination based MAC
entry entry’s MAC address, the packet will be forwarded to the ports as specified by the entry’s destination
mask;
• For a packet received from a port with its destination MAC address matching a destination based MAC
entry + dynamic entry’s MAC address, the packet will be forwarded to the source port specified in the
entry;
2.3.2.3 Port based forwarding
Port based forwarding is an additional mechanism to forward packets based on the port on which the packets
are received. This forwarding applies to all packets received, irrespective of their source and destination MAC
addresses.
Port based forwarding is the first level of forwarding applied to the received packets. The destination mask is
set to the forwarding mask of the port on which the packets are received. It serves the following purpose in
packet forwarding:
• If a source based MAC entry or a dynamic MAC entry matching the destination MAC address is found, the
packet is forwarded to the specified source port only if the port exists in the port forwarding mask of the
port on which packet is received.
• If a source based MAC entry matching the source MAC address is found, the packet is forwarded to all the
ports that exist in the destination mask as well as the port forwarding mask of the port on which packet is
received.
• If a destination based MAC entry, matching the destination MAC address is found, the packet is forwarded
to the all the ports that exist in the destination mask of the entry as well as the port forwarding mask of the
port on which packet is received.
2.3.2.4 Traffic Prioritization
The bridge module provides support for traffic prioritization in conformance to the IEEE 802.1p specifications.