Interface flaps observed after configuring the following command on an EX4650 device:

set chassis fpc 0 pic 0 port-range 48 55 channel-speed disable-auto-speed-detection

This command disables automatic speed detection on a specified range of ports and forces the interfaces to rely on manually configured speed and duplex settings.

After applying the configuration disable-auto-speed-detection, the following behavior may be observed:

• Interfaces in the specified port range momentarily go down and come back up

• Link flaps occur immediately after commit

• Traffic interruption is observed during the configuration change

• Syslog messages indicate link down/up events

On the EX4650 platform, the disable-auto-speed-detection option triggers a reinitialization of the PHY and port channel settings for the affected interfaces.

When this command is committed:

• Existing auto-negotiation parameters are removed

• The interface hardware is reprogrammed to disable speed detection

• The port must be reset to apply the new operational mode

This reset results in a temporary interface flap, which is expected behavior