MDS213 Datasheet, PDF (63/120 Pages) Zarlink Semiconductor Inc – 12-Port 10/100Mbps + 1Gbps Ethernet Switch

MDS213
Data Sheet
3-bit Hash Key
8 entries in table
Forwarding Port MASK Registers
(12 bits)
VLAN Member Port
AND
CPU sets up this table as follows:
1. Set up one entry of these registers at a
time until table is exhausted.
2. Set all bits not in any Trunk Group to 1.
3. Set all bits in the Trunk Groups to 0.
4. Pick one forwarding port per Trunk Group
and turn the corresponding bit to 1.
(Each Hash Key may have different forwarding
port, the rule to pick forwarding port is up to
CPU)
FP Mask
Forwarding Ports
Figure 24 - Forwarding Port Mask Table
Two restrictions exist in setting up tables:
1.
When setting up the VLAN Port Mapping Table, all the ports in the Trunk Group must be set to 1, if the
VLAN has ports in any Trunk Group.
2. When setting up the Forwarding Port Mask Table, the CPU software picks only one forwarding port per Trunk
Group.
17.2.2 Blocking Multicast Packets Back to the Source Trunk
For local multicast packets, the Frame Engine needs to block the multicast packets from being sent to the same
Trunk Group as the receiving (source) port. To do it, the Search Engine utilizes the Trunk Group ID (TGID) in ECR1
Register.
The Frame Engine compares the TGID of the source and forwarding ports. If the two TGIDs are the same, the
Frame Engine blocks the forwarding port for this multicast packet. The Switch Engine provides the TGID of the
source port.
Example
The following is an example demonstrating this port trunking scheme for multicast packet forwarding:
4 Trunk Group in a switch:
Group 0: port 0,1,2 in device 0
Group 1: port 4, 5,6 in device 0
Group 2: port 1, 2,3 in device 1
Group 3: port 4, 5,6 in device 1
A multicast packet with VLAN INDEX=5 is received at port 0 of device 0.
The membership of this VLAN:
Device 0: port 0,1,2, 4,5, 6, 7
Device 1: port 1,2, 3, 4,5,6, 8
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