Data Domain: LLDP Disabled by Default Starting DD OS 8.4 for Intel NIC Stability

Intermittent communication failures to the standby node after upgrading DD OS.
External devices are unable to consistently reach Node 0 through floating IP addresses or veth2.
HA status output shows the External LAN Heartbeat transitioning between "ok" and "not ok".
Random disconnections or communication interruptions despite interfaces being administratively up.
Frame drops observed on network interfaces with no corresponding hardware alerts.
LACP bonds fail to establish correctly or exhibit unstable behavior.
Intel X710/X710-derived interfaces unexpectedly disappear from the operating system or iDRAC when LACP negotiation fails.
Bonded interfaces experience transmit queue hangs or TX timeout events reported by the Intel i40e driver.
Excessive 802.1Qdd Priority Flow Control (PFC) traffic may be observed, potentially causing switch ports to shut down.
Failovers do not permanently resolve the issue.
Network connectivity issues begin after DD OS upgrades while no active Data Domain alerts are present.

Intel Ethernet 700 Series network adapters (including X710 and XXV710) contain a hardware-based LLDP engine that is enabled by default. The hardware LLDP engine consumes and responds to LLDP frames directly and does not forward these frames to the operating system network stack.
In environments using:

LACP (802.3ad)
Bonded interfaces
High Availability networking
Switch configurations that rely on LLDP information for proper LACP operation

the firmware LLDP engine can interfere with normal network protocol processing.
This may result in:

LACP negotiation failures
Bond instability
TX timeout conditions reported by the Intel i40e driver
Intermittent HA heartbeat failures
Standby node communication issues
Interface instability and unexpected link behavior

Field investigations identified that disabling the Intel firmware LLDP agent resolved multiple incidents involving TX timeouts and bonded interface failures. As a result, DD OS engineering implemented a change to disable firmware-based LLDP by default on supported Intel NICs.
For Intel 700 Series adapters, the setting disable-fw-lldp disables firmware handling of LLDP and allows the operating system to process LLDP frames.
For Intel 800 Series adapters (E810), the equivalent setting is fw-lldp-agent, which is disabled by default.

DD OS 8.4 and later releases disable the Intel firmware-based LLDP agent by default on supported adapters to prevent these networking issues.
Verify the system is running DD OS 8.4 or later. If running an earlier release and experiencing symptoms consistent with this issue, upgrade to a release that includes the LLDP default-disable behavior.
This change is applicable to Intel 700 Series NICs such as X710 and XXV710.
Additionally, ensure connected switches are correctly configured for LACP when using bonded interfaces. Incorrect switch-side LACP configuration can cause link establishment failures or unstable interface behavior regardless of LLDP settings.