Intel® IXP400 Software

Access-Layer Components: Ethernet Database (IxEthDB) API

An overview of the Egress tagging process is shown in Figure 55. The figure shows the decision tree for an untagged frame. The process is identical for a tagged frame.

Figure 55. Egress VLAN Control Path for Untagged Frames

EthAcc

EthDB

Outgoing frame (untagged)

Preamble

Start frame

Dest MAC addr

Src MAC addr

Len

 

 

 

 

 

Data

Pad FCS

Yes

Tagging override?

 

mbuf->ixp_ne_tx_flags.tag_over?

 

 

Untag

Tag frame?

Tag

Tag

 

 

 

 

 

mbuf->ixp_ne_tx_flags.tag_mode?

 

 

 

 

 

 

 

 

No

mbuf->ixp_ne_vlan_tci

Pri CFI VLAN ID

Check port TTI table for VLAN ID

Untag

VLAN 1

VLAN 2

VLAN 0

Tag

Untag

Untag

VLAN 4094

Tag

Tag frame with mbuf->ixp_ne_vlan_tci

Outgoing frame (802.1Q tagged)

Preamble

Start frame

Dest MAC addr

Src MAC addr

0x8100

Pri

 

 

 

 

 

 

CFI

VLAN ID

Len

 

 

 

Data

Pad

FCS

Tx

Table 28 presents an egress VLAN tagging/untagging behavior matrix.

Table 28. Egress VLAN Tagging/Untagging Behavior Matrix

Tag Mode (1)

Frame Status (2)

Action

Untag

Untagged

The NPE microcode does not modify the frame.

 

 

 

Untag

Tagged

The NPE microcode removes the VLAN tag from the frame.

 

 

 

April 2005

IXP400 Software Version 2.0

Programmer’s Guide

168

Document Number: 252539, Revision: 007

 

Page 168
Image 168
Intel IXP400 manual Egress Vlan Tagging/Untagging Behavior Matrix, Tag Mode Frame Status Action