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Network Position
Incoming Packet
TPID
Core
untagged
double-tag 0xUVWX 0xUVWX
Egress Access Point
untagged
double-tag 0xUVWX 0xUVWX
VLAN Stacking Packet Drop Precedence
VLAN stacking packet-drop precedence is supported on the switch.
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 69. Drop Eligibility Behavior
Ingress
Normal Port
Trunk Port
Access Port
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.
748
Service Provider Bridging
System TPID
0xUVWX
0xUVYZ
0xQRST
0xUVWX
0xUVYZ
0xQRST
Egress
Normal Port
Trunk Port
Trunk Port
Match Type
Pre-Version 8.2.1.0
—
switch to default
VLAN
double-tag match
switch to VLAN
double-tag first-byte
switch to VLAN
match
double-tag mismatch switch to default
VLAN
—
switch to default
VLAN
double-tag match
switch to VLAN
double-tag first-byte
switch to VLAN
match
double-tag mismatch switch to default
VLAN
DEI Disabled
Retain CFI
Retain inner tag CFI
Retain outer tag CFI
Retain inner tag CFI
Set outer tag CFI to 0
Version 8.2.1.0+
switch to default
VLAN
switch to VLAN
switch to default
VLAN
switch to default
VLAN
switch to default
VLAN
switch to VLAN
switch to default
VLAN
switch to default
VLAN
DEI Enabled
Set CFI to 0.
Retain inner tag CFI.
Set outer tag CFI to 0.
Retain inner tag CFI
Set outer tag CFI to 0
- Quick Links:
- Accessing the Command Line
- Cli Modes
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Troubleshooting
