1. Check the interface configuration, which is correct.
ip address dhcp-alloc
2. Check the interface status. It is found that the protocol of the interface is not Up.
3. Suspect that the rate negotiation is abnormal and check the detailed information about the interface. It is found that the interface is in auto-negotiation state.
4. Confirm with the customer about the IP address of the optical modem, which is 192.168.100.1. This IP address is the same as the one assigned to the intranet interface of the local device, causing an IP address conflict. After the IP address of the intranet interface on the local device is changed, the AR successfully obtains an IP address.
The IP addresses of the DHCP server and the intranet interface on the local device are in the same network segment. As a result, the router fails to obtain an IP address and the protocol status of the interface is not Up.
Change the IP address of the intranet interface on the local device.