Example 2 - Adapters Connected Through a Switch – Willing Mode on Adapters, DCB Configured on Switch

A common DCB strategy in a cluster is to configure DCB on the switches, then configure the adapters for willing mode. When the willing adapters are connected to a switch with DCB configured, the adapters automatically apply the same DCB configuration.

Settings in this example:

• Willing mode — Adapters use DCB settings from the link partner.
• Software LLDP — Recommended for willing mode.

Perform the following steps on all servers:

1. Disable LFC (LFC and PFC cannot co-exist). # ethtool -A <interface> rx off tx off
2. Verify that LFC is disabled. # ethtool -a <interface> Pause parameters for <interface>: Autonegotiate: on RX: off TX: off RX negotiated: off TX negotiated: off
3. Configure the adapter for firmware DCB mode (as opposed to software DCB mode. # ethtool --set-priv-flags <interface> fw-lldp-agent on
4. Verify that firmware DCB is enabled. # ethtool --show-priv-flags <interface> | grep fw-lldp-agent fw-lldp-agent : on
5. Configure DCB on the switch.

   Consult the appropriate switch manual for DCB configuration. You can configure PFC, ETS, or any combination.

6. Optional. Verify that the adapter is using the correct settings.

   Syntax varies by switch. In general, enable DCBX on the switch, then show the current DCBX information. The switch can then report how the attached adapter is configured.

   For example, from an Arista 7060CX:

   1. Enable DCBX in IEEE mode on port 21. switch#enable switch#configure switch(config)#interface Ethernet 21/1 switch(config-if-Et21/1)#dcbx mode ieee
   2. Show DCBX settings for port 21. (config-if-Et21/1)#show dcbx Ethernet 21/1 Ethernet21/1: IEEE DCBX is enabled and active Last LLDPDU received on Fri Feb 14 15:42:09 2020 - PFC configuration: willing capable of bypassing MACsec supports PFC on up to 8 traffic classes PFC not enabled on any priorities - Application priority configuration: 1 application priorities configured: ether 35078 priority 3
   Note:This output shows a combination of the switch port's own settings and the link partner's settings. It indicates that:
   • IEEE DCBX is active on the switch.
   • At the given timestamp, the switch port received an LLDPDU message from the link partner describing the link partner's DCB settings.
   • Everything after the Last LLDPU received line describes the contents of the received LLDPDU. These are the adapter’s settings.