L-ET4148-50C-DB LSI, L-ET4148-50C-DB Datasheet - Page 290

• Manufacturer Part Number: L-ET4148-50C-DB
• Manufacturer: LSI

Specifications of L-ET4148-50C-DB

• Lead Free Status / RoHS Status: Supplier Unconfirmed

ET4148-50
Preliminary Data Sheet
Single-Chip 48 x 1 Gbit/s + 2 x 10 Gbits/s Layer 2+ Ethernet Switch
April 2006
Appendix B: Configuration
(continued)
Other Networking Functions
This section describes the configuration requirements of a variety of additional packet handling methods supported
by the ET4148-50.
IGMP Snooping
IGMP snooping enables the copying of IGMP packets to the supervisor for processing. These snooped packets are
otherwise forwarded normally.
Each port may be individually enabled for IGMP snooping. This is accomplished by asserting the igmp_snoop_en
bit in the Layer_2_Mode register that corresponds to the receive port of interest. Once a port has been enabled to
have its receive traffic snooped for IGMP packets, all IGMP packets that are received have the port identified by the
Layer_2_Igmp_Snooping_Port added to the packet’s destination map. Typically, Layer_2_Igmp_Snooping_Port
is configured to identify one of the supervisor’s receive queues as the IGMP snooping port.
User-Port Snooping
User-port snooping makes it possible for the supervisor to receive copies of packets that are destined for a desig-
nated TCP or UDP destination port.
The TCP/UDP destination port number of interest is programmed into the Layer_2_User_Port register. Individual
Ethernet receive ports are enabled for user-port snooping by asserting their corresponding
user_port_snoop_en bits in the Layer_2_Mode register.
Packets received on the correctly enabled ports whose TCP or UDP destination port number matches the value in
Layer_2_User_Port are copied to the port identified by the Layer_2_User_Port_Snooping_Port register in
addition to being forwarded normally. Ordinarily, the user-port snooping port is chosen to be one of the supervisor’s
receive queues.
Cross-VLAN Routing
Communicating between VLANs typically requires the Layer 3 services of a router. The ET4148-50 includes the
capability to detect that a packet has been disallowed from being forwarded due to VLAN restrictions.
Individual ports may be enabled to support the cross-VLAN routing feature. This is done by asserting the
supervisor_route_en bits in the Layer_2_Mode register that correspond to the desired ports.
When a packet is received that ordinarily would have been forwarded to a transmit port if the destinations had not
been inhibited by VLAN restrictions, the supervisor route port is added to the packet’s destination map. This port is
designated via the Layer_2_Supervisor_Route_Port register.
Packets forwarded to the supervisor route port are expected to be routed by the supervisor to their appropriate
destinations.
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