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KSZ8765CLXIC View Datasheet(PDF) - Micrel

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KSZ8765CLXIC Datasheet PDF : 153 Pages
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Micrel, Inc.
KSZ8765CLX
IGMP Support
There are two components involved with the support of the Internet Group Management Protocol (IGMP) in Layer 2. The
first part is IGMP snooping, the second part is this IGMP packet which is sent back to the subscribed port. Those
components are described below.
IGMP Snooping: The KSZ8765CLX traps IGMP packets and forwards them only to the processor (Port 5 SW5-
RGMII/MII/RMII). 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. Set Register 5 bit [6] to ‘1’ to enable IGMP
snooping.
IGMP Send Back to the Subscribed Port: Once the host responds to the received IGMP packet the the host should
know the original IGMP ingress port and send back the IGMP packet to this port only. This prohibits the IGMP packet
from being broadcast to all ports, which will downgrade the performance. With tail tag mode enabled, the host will
know the port from which that IGMP packet has been received via tail tag bits [1:0] and can send back the response
IGMP packet to this subscribed port by setting bits [3:0] in the tail tag. Enable tail tag mode by setting Register 12 bit
[1].
IPv6 MLD Snooping
The KSZ8765CLX traps IPv6 multicast listener discovery (MLD) packets and forwards them only to the processor (Port 5).
MLD snooping is controlled by Register 164 bit [2] (MLD snooping enable) and Register 164 bit [3] (MLD option).
With MLD snooping enabled, the KSZ8765CLX traps packets that meet all of the following conditions:
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 the MLD option bit is set to “1”, the
KSZ8765CLX traps packets with the following additional condition:
IPv6 next header = 43, 44, 50, 51, or 60 (or = 0 with hop-by-hop next header = 43, 44, 50, 51, or 60)
For MLD snooping, tail tag mode also needs to be enabled, so that the processor knows on which port the MLD packet
was received. This is achieved by setting Register 12 bit [1].
Port Mirroring Support
The KSZ8765CLX supports port mirroring as described below:
“Receive Only” mirror on a port: All the packets received on the port will be mirrored on the sniffer port. For example,
Port 1 is programmed to be “RX sniff” and Port 5 is programmed to be the “sniffer port.” A packet, received on Port 1,
is destined to Port 4 after the internal look-up. The KSZ8765CLX will forward the packet to both Port 4 and Port 5.
KSZ8765CLX can optionally forward “bad” received packets to Port 5.
“Transmit Only” mirror on a port: All the packets transmitted on the port will be mirrored on the sniffer port. For
example, Port 1 is programmed to be “TX sniff,” and Port 5 is programmed to be the “sniffer port.” A packet, received
on any of the ports, is destined to Port 1 after the internal look-up. The KSZ8765CLX will forward the packet to both
Ports 1 and 5.
“Receive and Transmit” mirror on two ports: All the packets received on Port A and transmitted on Port B will be
mirrored on the sniffer port. To turn on the “AND” feature, set Register 5 bit [0] to 1. For example, Port 1 is
programmed to be “RX sniff,” Port 2 is programmed to be “TX sniff,” and Port 5 is programmed to be the “sniffer port.”
A packet, received on Port 1, is destined to Port 4 after the internal look-up. The KSZ8765CLX will forward the packet
to Port 4 only, because it does not meet the “AND” condition. A packet, received on Port 1, is destined to Port 2 after
the internal look-up. The KSZ8765CLX will forward the packet to both Port 2 and Port 5.
Multiple ports can be selected to be “RX sniff” or “TX sniff.” Any port can be selected to be the “sniffer port.” All these per
port features can be selected through the Port Control 1 Register.
July 23, 2014
48
Revision 1.0
 

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