Reference Guide

Network Position Incoming Packet
TPID
System TPID Match Type Pre-Version
8.2.1.0
Version 8.2.1.0+
0x81XY single-tag first-
byte match
switch to VLAN switch to default
VLAN
Core untagged 0xUVWX — switch to default
VLAN
switch to default
VLAN
double-tag
0xUVWX
0xUVWX double-tag match switch to VLAN switch to VLAN
0xUVYZ double-tag first-
byte match
switch to VLAN switch to default
VLAN
0xQRST double-tag
mismatch
switch to default
VLAN
switch to default
VLAN
Egress Access
Point
untagged 0xUVWX — switch to default
VLAN
switch to default
VLAN
double-tag
0xUVWX
0xUVWX double-tag match switch to VLAN switch to VLAN
0xUVYZ double-tag first-
byte match
switch to VLAN switch to default
VLAN
0xQRST double-tag
mismatch
switch to default
VLAN
switch to default
VLAN
VLAN Stacking Packet Drop Precedence
VLAN stacking packet drop precedence is available on the S4820T platform.
The drop eligible indicator (DEI) bit in the S-Tag indicates to a service provider bridge which packets it should prefer to
drop when congested.
Enabling Drop Eligibility
Enable drop eligibility globally before you can honor or mark the DEI value.
When you enable drop eligibility, DEI mapping or marking takes place according to the defaults. In this case, the CFI is
affected according to the following table.
Table 67. Drop Eligibility Behavior
Ingress Egress DEI Disabled DEI Enabled
Normal Port Normal Port Retain CFI Set CFI to 0.
Trunk Port Trunk Port Retain inner tag CFI Retain inner tag CFI.
Retain outer tag CFI Set outer tag CFI to 0.
Access Port Trunk Port Retain inner tag CFI Retain inner tag CFI
Set outer tag CFI to 0 Set outer tag CFI to 0
To enable drop eligibility globally, use the following command.
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