Users Guide

Data Center Bridging Exchange Protocol (DCBx)
The data center bridging exchange (DCBx) protocol is disabled by default on any switch on which PFC or ETS are enabled.
DCBx allows a switch to automatically discover DCB-enabled peers and exchange conguration information. PFC and ETS use DCBx to
exchange and negotiate parameters with peer devices. DCBx capabilities include:
• Discovery of DCB capabilities on peer-device connections.
• Determination of possible mismatch in DCB conguration on a peer link.
• Conguration of a peer device over a DCB link.
DCBx requires the link layer discovery protocol (LLDP) to provide the path to exchange DCB parameters with peer devices. Exchanged
parameters are sent in organizationally specic TLVs in LLDP data units. For more information, refer to Link Layer Discovery Protocol
(LLDP). The following LLDP TLVs are supported for DCB parameter exchange:
PFC parameters PFC Conguration TLV and Application Priority Conguration TLV.
ETS parameters ETS Conguration TLV and ETS Recommendation TLV.
Creating a DCB Map
Congure the priority-based ow control (PFC) and enhanced trac selection (ETS) settings in a DCB map before you can apply them on
downstream server-facing ports.
NOTE
: This feature is supported only on PMUX mode.
1 Create a DCB map to specify the PFC and ETS settings for groups of dot1p priorities.
CONFIGURATION mode
dcb-map name
2 Congure the PFC setting (on or o) and the ETS bandwidth percentage allocated to trac in each priority group or whether priority
group trac should be handled with strict priority scheduling.
DCB MAP mode
priority-group group_num {bandwidth percentage | strict-priority} pfc {on | off}
3 Specify the priority group ID number to handle VLAN trac for each dot1p class-of-service: 0 through 7. Leave a space between each
priority group number.
DCB MAP mode
priority-pgid dot1p0_group-num dot1p1_group-num dot1p2_group-num dot1p3_group-num
dot1p4_group-num dot1p5_group-num dot1p6_group-num dot1p7_group-num
Important Points to Remember
• If you remove a dot1p priority-to-priority group mapping from a DCB map (the no priority pgid command), the PFC and ETS
parameters revert to their default values on the interfaces on which the DCB map is applied. By default, PFC is not applied on specic
802.1p priorities; ETS assigns equal bandwidth to each 802.1p priority.
• To change the ETS bandwidth allocation congured for a priority group in a DCB map, do not modify the existing DCB map
conguration. Instead, rst create a new DCB map with the desired PFC and ETS settings and apply the new map to the interfaces to
override the previous DCB map settings. Then delete the original dot1p priority-priority group mapping.
Data Center Bridging (DCB)
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