VSC7511 datasheet(118/324 Pages) MICROSEMI

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Functional Descriptions

VMDS-10488 VSC7511 Datasheet Revision 4.2

103

Entries in the MAC table can be added, deleted, or updated in three ways:

•

Hardware-based learning of source MAC addresses (that is, inserting new (MAC, VID) pairs in the

MAC table).

•

Age scans (setting AGED_FLAG and deleting entries).

•

CPU commands (for example, for CPU-based learning).

3.9.1.1

Hardware-Based Learning

The analyzer adds an entry to the MAC table when learning is enabled, and the MAC table does not

contain an entry for a received frame’s (SMAC, VID). The new entry is formatted as follows:

•

VALID is set.

•

MAC is set to the frame’s SMAC.

•

VID is set to the frame’s VID prepended with 0.

•

ENTRY_TYPE is set to 0 (normal entry subject to aging).

•

DEST_IDX is set to the frame’s LPORT.

•

MAC_CPU_COPY is set to AGENCTRL.LEARN_CPU_COPY.

•

SRC_KILL is set to AGENCTRL.LEARN_SRC_KILL.

•

IGNORE_VLAN is set to AGENCTRL.LEARN_IGNORE_VLAN.

•

All other fields are cleared.

When a frame is received from a known station, that is, the MAC table already contains an entry for the

received frame’s (SMAC, VID), the analyzer can update the entry as follows.

For entries of entry type 0 (unlocked entries):

•

The AGED_FLAG is cleared. This implies the station is active, avoiding the deletion of the entry due

to aging.

•

If the existing entry’s DEST_IDX differs from the frame’s LPORT, then the entry’s DEST_IDX is set to

the frame’s LPORT. This implies the station has moved to a new port.

For entries of entry type 1 (locked entries):

•

The AGED_FLAG is cleared. This implies the station is active.

Entries of entry types 2 and 3 are never updated, because their multicast MAC addresses are never used

as source MAC addresses.

For more information about learning, see SMAC Analysis, page 114.

3.9.1.2

Age Scan

The analyzer scans the MAC table for inactive entries. An age scan is initiated by either a CPU command

or automatically performed by the device with a configurable age scan period (AUTOAGE). The age scan

ENTRY_TYPE

Entry type:

0: Normal entry subject to aging.

1: Normal entry not subject to aging (locked).

2: IPv4 multicast entry not subject to aging. Full port set is encoded in

MAC table entry.

3: IPv6 multicast entry not subject to aging. Full port set is encoded in

MAC table entry.

AGED_FLAG

Entry is aged once by an age scan. See Age Scan, page 103.

MAC_CPU_COP

Copy frames from or to this station to the CPU.

SRC_KILL

Do not forward frames from this station.

Note: This flag is not used for destination lookups.

IGNORE_VLAN

Do not use the VLAN_PORT_MASK from the VLAN table when

forwarding frames to this station.

Table 74 •

MAC Table Entry (continued)

Field

Bits

Description

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