Service Manual

Network Position Incoming Packet
TPID
System TPID Match Type Pre-Version 8.2.1.0 Version 8.2.1.0+
double-tag
0xUVWX
0xUVWX double-tag match switch to VLAN switch to VLAN
0xUVYZ double-tag rst-
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 rst-
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
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 aected
according to the following table.
Table 56. 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.
• Make packets eligible for dropping based on their DEI value.
CONFIGURATION mode
dei enable
By default, packets are colored green, and DEI is marked 0 on egress.
Honoring the Incoming DEI Value
To honor the incoming DEI value, you must explicitly map the DEI bit to an Dell Networking OS drop precedence.
Precedence can have one of three colors.
686
Service Provider Bridging