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User complains about network connectivity due to port flapping, does Extreme support MDIX or Auto-MDIX feature on Extreme switches?

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TitleUser complains about network connectivity due to port flapping, does Extreme support MDIX or Auto-MDIX feature on Extreme switches?
Symptoms
  • User complaining about network connectivity loss
  • Port flapping is observed at different link speed of 10/100/1000 randomly
  • logs reflect changing speed for some ports.
 <Info:vlan.msgs.portLinkStateUp> Slot-1: Port 3:28 link UP at speed 1 Gbps and full-duplex
 <Info:vlan.msgs.portLinkStateDown> Slot-1: Port 3:28 link down
 <Info:vlan.msgs.portLinkStateUp> Slot-1: Port 3:28 link UP at speed 10 Mbps and full-duplex
 <Info:vlan.msgs.portLinkStateDown> Slot-1: Port 3:28 link down
 <Info:vlan.msgs.portLinkStateUp> Slot-1: Port 3:28 link UP at speed 1 Gbps and full-duplex
 <Info:vlan.msgs.portLinkStateDown> Slot-1: Port 3:28 link down
 <Info:vlan.msgs.portLinkStateUp> Slot-1: Port 3:28 link UP at speed 10 Mbps and full-duplex
 <Info:vlan.msgs.portLinkStateDown> Slot-1: Port 3:28 link down

 
Environment
Summit - Copper
BlackDiamond - Copper
EXOS
Cause
  • defective cable
  • Auto-Polarity disabled
  • NIC Power Management settings - sleep mode enabled.
Resolution
  1. The Auto-MDIX feature on Extreme is called "Auto-polarity".
This feature applies to only the 10/100/1000 BASE-T ports on the switch and copper medium on Summit combo ports. It is enabled by default on all the copper ports. You can change the settings with following command.
 
Configure ports <port_list> auto-polarity [off | on]
 
If you want to confirm the default value or changed polarity status on any given port, you can check it via ‘show port <port_number> info detail’ command. For example:
 
Port: 1:1
Virtual-router: VR-Default
Type: UTP
Random Early drop: Disabled
Admin state: Enabled with auto-speed sensing auto-duplex
Link State: Active, 100Mbps, full-duplex
Link Counter: Up 1 time(s)
VLAN cfg:
Name: Default, Internal Tag = 1(MAC-Based), MAC-limit = No-limit

 
...<truncated output>
 
Egress 802.1p Replacement: Disabled
NetLogin: Enabled
NetLogin authentication mode: Mac based
NetLogin port mode: MAC based VLANs
Smart redundancy: Enabled
Software redundant port: Disabled
auto-polarity: Enabled
  1.  If the cable is fine and there are no polarity issues but link is still flapping with different speeds, check the NIC properties.
Depending on the NIC vendors, some Networks Interface Cards have Sleep Mode under Power Settings or Power Management. When sleep mode is enabled, the device will sleep after being inactive for a while and speed will be dropped to 10Mb until the device is active again.
Such settings can also cause port speed fluctuation.
Additional notes

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