KSZ8842-16MBL-EVAL MICREL [Micrel Semiconductor], KSZ8842-16MBL-EVAL Datasheet - Page 45

• Manufacturer Part Number: KSZ8842-16MBL-EVAL
• Description: 2-Port Ethernet Switch with Non-PCI Interface
• Manufacturer: MICREL [Micrel Semiconductor]

IGMP Support
For Internet Group Management Protocol (IGMP) support in Layer 2, the KSZ8842M provides two components:
“IGMP” Snooping
identified as IP packets (either Ethernet IP packets, or IEEE 802.3 SNAP IP packets) with IP version = 0x4 and protocol
version number = 0x2.
“Multicast Address Insertion” in the Static MAC Table
Once the multicast address is programmed in the Static MAC Table, the multicast session is trimmed to the subscribed
ports, instead of broadcasting to all ports.
IPv6 MLD Snooping
The KSZ8842M traps IPv6 Multicast Listener Discovery (MLD) packets and forwards them only to the processor (host
port). MLD snooping is controlled by SGCR2[13] (MLD snooping enable) and SGCR2[12] (MLD option).
Setting SGCR2[13] causes the KSZ8842M to trap packets that meet all of the following conditions:
Port Mirroring Support
KSZ8842M supports “Port Mirroring” comprehensively as:
“receive only” mirror on a port
All the packets received on the port are mirrored on the sniffer port. For example, port 1 is programmed to be “receive
sniff” and the host port is programmed to be the “sniffer port”. A packet received on port 1 is destined to port 2 after the
internal lookup. The KSZ8842M forwards the packet to both port 2 and the host port. The KSZ8842M can optionally even
forward “bad” received packets to the “sniffer port”.
“transmit only” mirror on a port
All the packets transmitted on the port are mirrored on the sniffer port. For example, port 1 is programmed to be “transmit
sniff” and the host port is programmed to be the “sniffer port”. A packet received on port 2 is destined to port 1 after the
internal lookup. The KSZ8842M forwards the packet to both port 1 and the host port.
“receive and transmit” mirror on two ports
All the packets received on port A and transmitted on port B are mirrored on the sniffer port. To turn on the “AND” feature,
set register SGCR2, bit 8 to “1”. For example, port 1 is programmed to be “receive sniff”, port 2 is programmed to be
“transmit sniff”, and the host port is programmed to be the “sniffer port”. A packet received on port 1 is destined to port 2
after the internal lookup. The KSZ8842M forwards the packet to both port 2 and the host port.
Multiple ports can be selected as “receive sniff” or “transmit sniff”. In addition, any port can be selected as the “sniffer
port”. All these per port features can be selected through registers P1CR2, P2CR2, and P3CR2 for ports 1, 2, and the
host port, respectively.
IEEE 802.1Q VLAN Support
The KSZ8842M supports 16 active VLANs out of the 4096 possible VLANs specified in the IEEE 802.1Q specification.
KSZ8842M provides a 16-entry VLAN table, which converts the 12-bits VLAN ID (VID) to the 4-bits Filter ID (FID) for
address lookup. If a non-tagged or null-VID-tagged packet is received, the ingress port default VID is used for lookup. In
VLAN mode, the lookup process starts with VLAN table lookup to determine whether the VID is valid. If the VID is not
valid, the packet is dropped and its address is not learned. If the VID is valid, the FID is retrieved for further lookup. The
FID + Destination Address (FID+DA) are used to determine the destination port. The FID + Source Address (FID+SA) are
used for address learning. (See Tables 10 and 11.)
The KSZ8842M traps IGMP packets and forwards them only to the processor (host port). The IGMP packets are
Micrel, Inc.
October 2007
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IPv6 multicast packets
Hop count limit = 1
IPv6 next header = 1 or 58 (or = 0 with hop-by-hop next header = 1 or 58)
If SGCR2[12] = 1, IPv6 next header = 43, 44, 50, 51, or 60 (or =0 with hop-by-hop next header = 43, 44, 50, 51,
or 60)
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KSZ8842-16/32 MQL/MVL/MVLI/MBL
M9999-102207-1.9