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KSZ8873MLLJ Datasheet(PDF) 35 Page - Micrel Semiconductor |
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KSZ8873MLLJ Datasheet(HTML) 35 Page - Micrel Semiconductor |
35 / 108 page ![]() Micrel, Inc. KSZ8873MLLJ September 2011 35 M9999-091911-1.8 Ingress to Port 3 (Host -> KSZ8873MLLJ) Bit [1,0] Destination Port 0,0 Normal (Address Look up) 0,1 Port 1 1,0 Port 2 1,1 Port 1 and 2 Bit [3,2] Frame Priority 0,0 Priority 0 0,1 Priority 1 1,0 Priority 2 1,1 Priority 3 Egress from Port 3 (KSZ8873MLLJ->Host) Bit [0] Source Port 0 Port 1 1 Port 2 Figure 8. Tail Tag Rules IGMP Support For Internet Group Management Protocol (IGMP) support in layer 2, the KSZ8873MLLJ provides two components: IGMP Snooping The KSZ8873MLLJ traps IGMP packets and forwards them only to the processor (port 3). The IGMP packets are identified as IP packets (either Ethernet IP packets, or IEEE 802.3 SNAP IP packets) with IP version = 0x4 and protocol version number = 0x2. IGMP Send Back to the Subscribed Port Once the host responds the received IGMP packet, the host should knows the original IGMP ingress port and send back the IGMP packet to this port only, otherwise this IGMP packet will be broadcasted to all port to downgrade the performance. Enable the tail tag mode, the host will know the IGMP packet received port from tail tag bits [0] and can send back the response IGMP packet to this subscribed port by setting the bits [1,0] in the tail tag. Enable “Tail tag mode” by setting Register 3 bit 6. The tail tag will be removed automatically when the IGMP packet is sent out from the subscribed port. Port Mirroring Support KSZ8873MLLJ 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 port 3 is programmed to be the “sniffer port”. A packet received on port 1 is destined to port 2 after the internal lookup. The KSZ8873MLLJ forwards the packet to both port 2 and port 3. The KSZ8873MLLJ 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 port 3 is programmed to be the “sniffer port”. A packet received on port 2 is destined to port 1 after the internal lookup. The KSZ8873MLLJ forwards the packet to both port 1 and port 3. “receive and transmit” mirror on two ports |
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