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A customer has a HP Aruba Switch (i have no remote access, only via teamviewer) on which an interface goes up/down periodically. The customer has an ESX host connected to that interface, thats how he knew the port was flapping. I pulled down a diagnostics file

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and found that the interface threw error messages like

%Mar  1 14:39:13:724 2023 HV-CORE IFNET/3/PHY_UPDOWN: Ten-GigabitEthernet4/0/31 link status is up.
%Mar  1 14:39:13:725 2023 HV-CORE IFNET/5/LINK_UPDOWN: Line protocol on the interface Ten-GigabitEthernet4/0/31 is up.
%Mar  1 14:39:14:621 2023 HV-CORE LLDP/6/LLDP_CREATE_NEIGHBOR: -Slot=4; Nearest bridge agent new neighbor created on Port Ten-GigabitEthernet4/0/31 (IfIndex 646), Chassis ID is XXX, Port ID is XXX.

I guess the flapping is caused by LLDP? Would a solution be to disable LLDP on that port?

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    It is very, very unlikely that LLDP is the cause. If the port goes up it is perfectly normal that LLDP detect a new neighbor. This is a consequence, not a cause. But we don't have enough information to guess the real cause; I would start by checking the physical cabling. A loose cable could explain this.
    – JFL
    Mar 6, 2023 at 11:09
  • Thank you i will try to replace the cable.
    – MBrain
    Mar 6, 2023 at 12:31
  • You've only shown the port coming up, not going down. If you want to know what it's down, look for the reason it went down.
    – Ricky
    Mar 6, 2023 at 20:33

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LLDPDUs are sent in regular intervals and possibly a fixed time after a "link up" event. That log message just informs about a newly discovered neighbor (which might just have been cleared before on "link down"). A relation to the link flapping is highly unlikely. Of course, you can deactivate LLDP on that port but I wouldn't expect any change.

The log excerpt you provide isn't really an error message. The link-down event might provide more insight, as might any error or anomaly counters on the affected interfaces (both sides if possible).

For fiber interfaces you might also want to check for DOM information (show interface transceiver detail) regarding power output and receive levels (which might indicate an unsuitable or defect cable), module overtemp or similar.

If you need a quick solution, I'd swap ports (don't forget SFP+ modules) and cables and check whether the problem moves or vanishes. If it does, don't forget to check the previous, now out-of-production ports.

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  • Thank you i will try to replace the cable and see if it helps.
    – MBrain
    Mar 6, 2023 at 12:31

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