Reference Guide

Service Provider Bridging | 809
VLAN Stacking Packet Drop Precedence
VLAN Stacking Packet Drop Precedence is available on the S5000 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.
Enable Drop Eligibility
You must enable Drop Eligibility globally before you can honor or mark the DEI value.
When Drop Eligibility is enabled, DEI mapping or marking takes place according to the defaults. In this
case, the CFI is affected according to Table 45-2.
Egress Access Point untagged 0xUVWX — switch to default
VLAN
double-tag
0xUVWX
0xUVWX double-tag match switch to VLAN
0xUVYZ double-tag
first-byte match
switch to default
VLAN
0xQRST double-tag
mismatch
switch to default
VLAN
Task Command Syntax Command Mode
Make packets eligible for dropping based on their DEI value. By
default, packets are colored green, and DEI is marked 0 on egress.
dei enable
CONFIGURATION
Table 45-2. 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
Table 45-1. S5000 Behavior for Mis-matched TPID
Network
Position
Incoming
Packet TPID
System
TPID Match Type 9.1(1.0)