Data Centre Bridging Capability Exchange Configuration
Overview
The Data Center Bridging Capability Exchange (DCBX) protocol is an extension of the Link Layer Discovery Protocol (LLDP). It facilitates the exchange of Data Center Bridging (DCB) configuration parameters between directly connected devices, such as switches and network interface cards (NICs). DCBX enables automatic negotiation and configuration of DCB features to ensure consistent quality of service (QoS) and traffic prioritization across a network.
If LLDP is disabled on an interface, DCBX cannot operate on that interface. Attempting to enable DCBX on an interface where LLDP is disabled will result in a configuration commit failure.
DCBX plays a crucial role in modern data centers by enabling seamless configuration and interoperability between DCB-capable devices, ensuring efficient network performance.
Benefits
• Discovers the DCB capabilities of neighboring devices.
• Detects incorrect configurations or mismatches in DCB settings between peers.
• Configures DCB parameters on connected devices for interoperability.
Protocols Supported for DCBX
DCBX is primarily used to manage the following DCB protocols:
Priority-based Flow Control (PFC)
Provides flow control per traffic class, reducing packet loss in congestion-sensitive applications like storage and high-performance computing.
Topology
DCBx Configurat ion
Configuring PFC Parameter Exchange
SW2
#configure terminal | Enter configure mode |
(config)#bridge 1 protocol ieee vlan-bridge | Create bridge 1 as an IEEE VLAN-enabled bridge |
(config)#data-center-bridging enable bridge 1 | Enable DCB on the bridge |
(config)#priority-flow-control enable bridge 1 | Enable PFC on the bridge |
(config)#interface eth1 | Configure interface eth1 |
(config-if)#switchport | Configure eth1 as a layer 2 port |
(config-if)#bridge-group 1 | Configure eth1 in bridge group 1 |
(config-if)#lldp-agent | Enter into LLDP agent mode. |
(lldp-agent)#set lldp enable txrx | Configure LLDP for transmit and receive mode on eth1 |
(lldp-agent)#lldp tlv-select ieee-8021-org-specific | Configure LLDP to send an IEEE 802.1 organizationally specific TLV set in the packet |
(lldp-agent)#exit | Exit from LLDP mode. |
(config-if)#priority-flow-control mode on | Configure the advertise flag and start sending DCBx TLVs in LLDP messages |
(config-if)#priority-flow-control cap 4 | Configure the maximum number of PFC priorities |
(config-if)#priority-flow-control enable priority 2 4 5 | Enables PFC on priorities 2,4, and 5 |
(config-if)#priority-flow-control link-delay-allowance 34567 | Configure the link delay allowance |
SW1
#configure terminal | Enter configure mode |
(config)#bridge 1 protocol ieee vlan-bridge | Create bridge 1 as an IEEE VLAN-enabled bridge |
(config)#data-center-bridging enable bridge 1 | Enable DCB on the bridge |
(config)#priority-flow-control enable bridge 1 | Enable PFC on the bridge |
(config)#interface eth1 | Configure interface eth1 |
(config-if)#switchport | Configure eth1 as a layer 2 port |
(config-if)#bridge-group 1 | Configure eth1 in bridge group 1 |
(config-if)#lldp-agent | Enter into LLDP agent mode. |
(lldp-agent)#set lldp enable txrx | Configure LLDP for transmit and receive mode on eth1 |
(lldp-agent)#lldp tlv-select ieee-8021-org-specific | Configure LLDP to send an IEEE 802.1 organizationally specific TLV set in the packet |
(lldp-agent)#exit | Exit from LLDP mode. |
(config-if)#priority-flow-control mode on | Configure the advertise flag and start sending DCBx TLVs in LLDP messages |
(config-if)#priority-flow-control cap 4 | Configure the maximum number of PFC priorities |
(config-if)#priority-flow-control enable priority 2 4 5 | Enables PFC on priorities 2,4, and 5 |
(config-if)#priority-flow-control link-delay-allowance 34567 | Configure the link delay allowance |
Validation
SW1
Verify the data set.
#show priority-flow-control details interface eth1
bridge : 1
priority flow control : on
interface : eth1
Admin Configuration
mode advertise willing cap link priorities
delay
allowance
==============================================================================
on on off 4 34567 2 4 5
Operational Configuration
state cap link priorities
delay
allowance
==============================================================================
on 4 34567 2 4 5
SW2
Verify the data set.
#show priority-flow-control details interface eth1
bridge : 1
priority flow control : on
interface : eth1
Admin Configuration
mode advertise willing cap link priorities
delay
allowance
================================================================================
on on off 4 34567 2 4 5
Operational Configuration
state cap link priorities
delay
allowance
================================================================================
on 4 34567 2 4 5