zl50400 Zarlink Semiconductor, zl50400 Datasheet - Page 32

• Manufacturer Part Number: zl50400
• Description: Lightly Managed/unmanaged 9-port 10/100 M Ethernet Switch
• Manufacturer: Zarlink Semiconductor

5.3
5.3.1
The search block performs source MAC address and destination MAC address searching. As we indicated earlier,
if a match is not found, then the next entry in the linked list must be examined, and so on until a match is found or
the end of the list is reached.
In port based VLAN mode, a bit map is used to determine whether the frame should be forwarded to the outgoing
port. The main difference in this mode is that the bit map is not dynamic. Ports cannot enter and exit groups
because of real-time learning made by a CPU.
The MAC search block is also responsible for updating the source MAC address timestamp used for aging.
5.3.2
The learning module learns new MAC addresses and performs port change operations on the MCT database. The
goal of learning is to update this database as the networking environment changes over time.
When CPU reporting is enabled, learning and port change will be performed when the CPU request queue has
room, and a “Learn MAC Address” message is sent to the CPU.
5.3.3
Aging time is controlled by register 400h and 401h.
The aging module scans and ages MCT entries based on a programmable “age out” time interval. As we indicated
earlier, the search module updates the source MAC address timestamps for each frame it processes. When an
entry is ready to be aged, the entry is removed from the table, and a “Delete MAC Address” message is sent to
inform the CPU.
Supported MAC entry types are: dynamic, static, source filter, destination filter, source and destination filter, secure
and multicast MAC address. Only dynamic entries can be aged; all others are static. The MAC entry type is stored
in the “status” field of the MCT data structure.
5.4
The ZL50400's implementation of intelligent traffic switching provides filters for source and destination MAC
addresses. This feature filters unnecessary traffic, thereby providing intelligent control over traffic flows and
broadcast traffic.
MAC address filtering allows the ZL50400 to block an incoming packet to an interface when it sees a specified MAC
address in either the source address or destination address of the incoming packet. For example, if your network is
congested because of high utilization from a MAC address, you can filter all traffic transmitted from that address
and restore network flow, while you troubleshoot the problem.
5.5
Packet filtering can be performed based on protocol type field in the packets. Up to eight protocols can be
programmed to filter or allow packet to pass through the switch.
5.6
Similar to protocol filtering, if the packet’s logical ports match the programmable registers, the packet can be filtered
or passed through the switch. Up to eight programmable ports and one ranges can be assigned.
Search, Learning, and Aging
MAC Address Filtering
Protocol Filtering
Logical Port Filtering
MAC Search
Learning
Aging
Zarlink Semiconductor Inc.
ZL50400
32
Data Sheet