ZL50418GKC ZARLINK [Zarlink Semiconductor Inc], ZL50418GKC Datasheet - Page 41

• Manufacturer Part Number: ZL50418GKC
• Description: Managed 16-Port 10/100 M + 2-Port 1 G Ethernet Switch
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

8.0
8.1
A port group (i.e., trunk) can include up to 4 physical ports, but when using stack all of the ports in a group must be
in the same ZL50418.
The two Gigabit ports may also be trunked together. There are three trunk groups total, including the option to trunk
Gigabit ports.
Load distribution among the ports in a trunk for unicast is performed using hashing based on source MAC address
and destination MAC address. Three other options include source MAC address only, destination MAC address
only and source port (in bidirectional ring mode only). Load distribution for multicast is performed similarly.
If a VLAN includes any of the ports in a trunk group, all the ports in that trunk group should be in the same VLAN
member map.
The ZL50418 also provides a safe fail-over mode for port trunking automatically. If one of the ports in the trunking
group goes down, the ZL50418 will automatically redistribute the traffic over to the remaining ports in the trunk in
unmanaged mode. In managed mode, the software can perform similar tasks.
8.2
The search engine finds the destination MCT entry and if the status field says that the destination port found
belongs to a trunk, then the group number is retrieved instead of the port number. In addition, if the source address
belongs to a trunk, then the source port’s trunk membership register is checked.
A hash key, based on some combination of the source and destination MAC addresses for the current packet,
selects the appropriate forwarding port, as specified in the Trunk_Hash registers.
8.3
For multicast packet forwarding, the device must determine the proper set of ports from which to transmit the
packet based on the VLAN index and hash key.
Two functions are required in order to distribute multicast packets to the appropriate destination ports in a port
trunking environment.
Determining one forwarding port per group.
Preventing the multicast packet from looping back to the source trunk.
The search engine needs to prevent a multicast packet from sending to a port that is in the same trunk group with
the source port. This is because, when we select the primary forwarding port for each group, we do not take the
source port into account. To prevent this, we simply apply one additional filter so as to block that forwarding port for
this multicast packet.
8.4
In unmanaged mode, 3 trunk groups are supported. Groups 0 and 1 can trunk up to 4 10/100 ports. Group 2 can
trunk 2 Gigabit ports. The supported combinations are shown in the following table.
Features and Restrictions
Unicast Packet Forwarding
Multicast Packet Forwarding
Unmanaged Trunking
Port Trunking
Group 0
Table 13 - Select via trunk0_mode register
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Port 0
Zarlink Semiconductor Inc.
ZL50418
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Port 1
Port 2
Port 3
Data Sheet