Allied Telesis 2.6.1 manual Layer 2 Filtering

Layer 2 Switching 83

the switch floods the frame on all ports in the VLAN except the port on which the frame was received. If the destination address is found, the switch discards the frame if the port is not in the STP ‘Forwarding’ state, if the destination address is on the same port as the source address, or if there is a static filter entry for the destination address set to DISCARD (“Layer 2 Filtering” on page 83). Otherwise, the frame is forwarded on the indicated port.

This whole process can further be modified by the action of static switch filters. These are configurable filters which allow switched frames to be checked against a number of entries.

The Forwarding Process provides storage for queued frames to be transmitted over a particular port or ports. More than one transmission queue may be provided for a given port. Which transmission queue a frame is sent to is determined by the user priority tag in the Ethernet frame, and the Quality of Service mapping.

Layer 2 Filtering

The switch has a Forwarding Database, entries in which determine whether frames are forwarded or discarded over each port. Entries in this Forwarding Database are created dynamically by the Learning Process. A dynamic entry is automatically deleted from the Forwarding Database when its ageing timer expires. Filtering is specified in the IEEE 802.1D Standard “Media Access Control (MAC) Bridges”.

The user can configure static switch filter entries using the command line interface. Static switch filter entries associate a MAC address with a VLAN and a port in the VLAN. When the switch receives a frame with a destination address and VLAN Identifier that match those of a static filter entry, the frame can be either forwarded to the port specified in the static filter entry, or discarded.

The Forwarding Database supports queries by the Forwarding Process as to whether frames with given values of the destination MAC address field should be forwarded to a given port.

To add or delete static switch filter entries, use the commands:

ADD SWITCH FILTER DESTADDRESS=macadd ACTION={FORWARDDISCARD}

PORT[=port-list] [ENTRY=entry] [VLAN={vlanname1..4094}]

DELETE SWITCH FILTER ENTRY=entry-list

The switch automatically deletes static filter entries for a port if the port is deleted from the specified VLAN.

To display current static switch filter entries, use the command:

SHOW SWITCH FILTER [DESTADDRESS=macadd] [ENTRY=entry] [PORT=port-list] [VLAN={vlanname1..4094}]

Software Release 2.6.1 C613-02039-00 REV A