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Interface ends up in port state is disabled after several hours of flaps and does not pass traffic

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TitleInterface ends up in port state is disabled after several hours of flaps and does not pass traffic
The 100G port 31/2(LAG primary) started to flap and then became "port state is Disabled" however it is in UP/UP state as shown below.

100GigabitEthernet31/2 is up, line protocol is up
Loopback: None
STP Root Guard is disabled, STP BPDU Guard is disabled
Hardware is 100GigabitEthernet, address is 0024.3897.79a1 (bia 0024.3897.79a1)
Configured speed 100Gbit, actual 100Gbit, configured duplex fdx, actual fdx
Member of Control VLAN 4095, VLAN 900 (untagged), port is in untagged mode, port state is Disabled
STP configured to ON, Priority is level0, flow control enabled
Priority force disabled, Drop precedence level 0, Drop precedence force disabled
dhcp-snooping-trust configured to OFF
mirror disabled, monitor disabled
LACP BPDU Forwarding:Disabled
LLDP BPDU Forwarding:Disabled


The link kept on flapping for around 17 hours before it was stabilized but does not forward traffic.

Software Release: N/A
Fixed in Version: NI 6.1.0
The problem is due to the command "delay-link-event" as you can see in the interface configuration above. The "delay-link-event 50" is a port transition hold timer.While link down events are reported immediately in syslog, their effect on higher level protocols such as OSPF is delayed according to how the delay-link-event is configured.

The command "delay-link-event" is impacted by a software problem and thus unable to correctly maintain the timer which keeps the link with "port state is Disabled" forever. Therefore, the link does not pass any traffic although physically up.
The software defect will be fixed in future release and will be documented in the release notes.
Additional notes
Since the issue is caused by the delay-link-event, the workaround is simply to remove this command from the interface configuration. Of course, this defeats the purpose of having this command.



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