AL103 Revision 1.0
3.5 Address Learning
The Table Lookup Engine provides the switching information required to route data frames. The
address lookup table is set-up through auto address learning (dynamic) or manual entry (static). The
static addresses are assigned to the address table by the EEPROM. All static address entries will not
be aged or updated by the AL103.
After a frame is received by the AL103, the embedded (SA) and destination address (DA) are
retrieved. The source address retrieved from the received frame is automatically stored in a SA
buffer. The AL103 will then check for error and security violations, and perform a SA search. If
there is no error or security violation, the AL103 will store the source address in the address lookup
table. If the SA has been previously stored in another port’s SA table, the AL103 will delete the SA
from the previously stored location.
The Individual MAC Address is a 48-bit unique MAC address to be programmed or learned. Bit 0
of a SA will be masked, i.e. no multicast SA.
The AL103 provides an on-chip 1K MAC Address-to-PortID/TrunkID table for the frame
destination lookup operations.
The AL103 address table contains both static addresses input by the EEPROM and dynamically
learned address. It learns the individual MAC addresses from frame received with no errors from
the local ports.
For received frames that contain a source address learned in another port’s address table, that hasn’t
been aged out, perform the following based on the switches; if the security option is selected for the
port, the AL103 considers this a security violation; if port is a non-protected port, the AL103 will
delete the SA from the previous port’s address table and update it to the current port’s address table.
However, if the SA is a static address entry, the address will not be updated.
3.5.1 Address Aging
A port’s MAC address register is cleared on power-up, or hardware reset. If the SA aging option is
enabled, the dynamically learned SA will be cleared if it is not refreshed within the programmed
time.
3.6 VLAN Support
Each port of the AL103 can be assigned to one or multiple VLANs. Frames from the source port
will only be forwarded to destination ports within the same VLAN domain. A broadcast/multicast
frame will be forwarded to all ports within the VLAN(s) except the source port itself. A unicast
frame will be forwarded to the destination port only if the destination port is in the same VLAN as
the source port. Otherwise, the frame will be treated as a frame with unknown DA. If the
destination port belongs to the another VLAN, the frame will be discarded and the event will be
recorded as a VLAN boundary violation.
Each port can be assigned with a dedicated uplink port. Unicast frames with unknown destination
addresses will be forwarded to the uplink port of the source port. An uplink port can be either a
single port or a trunk.
The AL103 provides one VLAN register per ports (register 1E to 2C) for mapping to 8-ports (8-
bits). Each register contains an 8-bit map to indicate the VLAN group for the port.
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