What can I do if an interface on a PPPoE client frequently alternates between Up and Down states

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The possible causes are as follows:



    -The IP address assigned to the interface by the PPPoE server is the same as that of another interface on the PPPoE client.


    Solution: Change the conflicting IP address on the PPPoE client or run the remote address command on the PPPoE server to change the IP address assigned to the interface.



  • -All IP addresses in the address pool on the PPPoE server have been allocated to PPPoE clients and no IP address is available for this interface.


    Solution: Run the network (IP address pool view) command in the IP address pool view on the PPPoE server to expand the IP address range of the IP address pool.

Other related questions:
How to handle the problem that the state of an interface alternates between Up and Down frequently after the PPP protocol negotiation is complete
This problem occurs because the PPP protocol link detection packets cannot be sent or received properly due to large traffic. Solution: Run the timer hold 0 command on the interfaces configured with the PPP service to disable the PPP protocol sending link detection packets.

The PPPoE physical interface is Up but the state of the protocol is Down
After a PPPoE dialup, all services are born on the Dialer interface, with corresponding physical interface being Up and protocol being Down, which is normal and does not affect the services and use. Ignore it. A virtual interface is needed for PPPoE dialup to bear all services. Pay attention to the Dialer interface, and the protocol status does not need to be concerned with.

The state of an E1 interface is not Up when the interface interconnects with the peer device
For the problem that the state of an E1 interface of an AR router is not Up when the interface interconnects with other devices, see the troubleshooting guide. For details, access the URL in the right column.

An interface on a WLAN device goes Up or Down frequently
The possible causes are as follows: - The power cable is faulty or the optical fiber does not meet requirements. - The duplex modes, rates, and negotiation modes are different on the connected interfaces. - The device hardware is faulty. Perform the following operations to rectify the fault: 1. If the interface is an electrical interface or a combo interface working in electrical mode, check whether the power cable is faulty and securely connected on the local and remote devices. If the interface is an optical interface or a combo interface working in optical mode, check whether the type and length of the optical fiber, and the transmission distance supported by the optical module meet requirements. 2. Run the display interface [ interface-type [ interface-number ] ] command to check the rate, duplex mode, and negotiation mode of the interface. In the command, interface-type and interface-number specify the interface type and number, respectively. - Check the Negotiation field. If ENABLE is displayed, the interface works in auto-negotiation mode. If DISABLE is displayed, the interface works in non-auto-negotiation mode. The two interfaces on the local and remote devices must work in the same negotiation mode (auto-negotiation or non-auto-negotiation mode). You can run the negotiation auto command in the interface view to configure an interface to work in auto-negotiation mode. If the fault persists, configure the interface to work in non-auto-negotiation mode, and forcibly set the same rate and duplex mode for the interconnected interfaces. - Check the Speed field. If the rates of the interfaces on the local and remote devices are different, run the speed command in the interface view to set the same rate for the two interfaces. - Check the Duplex field. If the duplex modes of the interfaces on the local and remote devices are different, run the duplex command in the interface view to set the same duplex mode for the two interfaces. 3. Perform a loopback test on the AC using an Ethernet cable to connect the interface to another interface. If the interface can go Up, the WLAN is working properly. The remote device may be faulty. Contact the vendor of the remote device to rectify the fault. - If an electrical interface or a combo interface working in electrical mode cannot go Up, change it to another interface. If an optical interface or a combo interface working in optical mode cannot go Up, replace the optical module.

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