TNETX15VE datasheet(108/113 Pages) TI1

108 / 113 page

TNETX15VE

VLAN-ENGINE ADDRESS-LOOKUP DEVICE

SPWS028B – APRIL 1997 – REVISED SEPTEMBER 1997

108

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

TNETX15VE VLAN support

The TNETX15VE supports VLAN through its VLANmask, tagVLAN, and VLANID registers. Using these

registers, the user can associate each port to a specific VLAN and set the routing options for each VLAN when

the address is not found within the lookup table.

The VLANID registers give the VLAN assignment of the ports for the TNETX3150/TNETX3150A that a

TNETX15VE is attached to. The tagVLAN registers can be used to either mirror a cascaded

TNETX3150/TNETX3150A VLAN port assignment or as a user-defined code that is passed through the uplink

(port 00). The VLANmask registers are used to set the routing options for unknown addresses and to mask out

multicast-address routing when they are found within the lookup table.

VLAN support for cascaded systems

When two TNETX3150/TNETX3150As are connected in a cascaded system, the VLAN assignment ordinarily

is lost when frames traverse through the uplink. To solve this problem, each TNETX3150/TNETX3150A pretags

the frame with the source port number. This pretag is shown in the DRAM bus and decoded by the TNETX15VE.

Thus, the TNETX15VE knows the source port number for the remote system.

To tie the remote source port number to a VLANID, each TNETX15VE uses the tagVLAN registers. In the

TNETX3150/TNETX3150A

cascaded

systems,

the

tagVLAN

registers

enable

one

TNETX3150/TNETX3150A’s TNETX15VE to mirror its TNETX15VE counterpart in the cascaded

TNETX3150/TNETX3150A. The tagVLAN registers are set up with the VLANID registers of its partner. Thus,

the TNETX15VE No. 1 knows the VLAN assignments for the TNETX15VE No. 2 tables, and vice versa.

The following charts describe how to set up the individual VLAN registers for a cascaded system. TagVLAN0

is a don’t care because it maps to the remote TNETX3150/TNETX3150A port 00 that is shared (i.e., in this

application there are no frames sourced by the network coming from port 00).

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