User Manual

When DCB is Disabled (Default) By default, Aggregator interfaces operate with DCB disabled and link-
level flow control enabled. When an interface comes up, it is automatically configured with:
• Flow control enabled on input interfaces.
• A DCB-MAP policy is applied with PFC disabled.
The following example shows a default interface configuration with DCB disabled and link-level flow
control enabled.
show interfaces Command Example: DCB disabled and Flow Control enabled
Dell#show running-config interface te 0/4
!
interface TenGigabitEthernet 0/4
mtu 12000
portmode hybrid
switchport
auto vlan
flowcontrol rx on tx off
dcb-map DCB_MAP_PFC_OFF
!
protocol lldp
advertise management-tlv management-address system-name
dcbx port-role auto-downstream
no shutdown
Dell#
When DCB is Enabled When an interface receives a DCBx protocol packet, it automatically enables DCB
and disables link-level flow control. The dcb-map and flow control configurations are removed as shown
in the following example.
show interfaces Command Example: DCB enabled and Flow Control disabled
Dell#show running-config interface te 0/3
!
interface TenGigabitEthernet 0/3
mtu 12000
portmode hybrid
switchport
auto vlan
!
protocol lldp
advertise management-tlv management-address system-name
dcbx port-role auto-downstream
no shutdown
Dell#
When no DCBx TLVs are received on a DCB-enabled interface for 180 seconds, DCB is automatically
disabled and flow control is re-enabled.
Lossless Traffic Handling In auto-DCB-enable mode, Aggregator ports operate with the auto-detection
of DCBx traffic. At any moment, some ports may operate with link-level flow control while others operate
with DCB-based PFC enabled.
As a result, lossless traffic is ensured only if traffic ingresses on a PFC-enabled port and egresses on
another PFC-enabled port.
Data Center Bridging (DCB)
35