DHCP troubleshooting steps

In the previous article, we have explained the DHCP fault handling process and some illustration results. I believe you should be impressed with this. Based on the previous figure, we will explain the DHCP troubleshooting steps. There are three major steps in total, some of which can be mastered.

Procedure

DHCP troubleshooting Step 1. Check whether the physical connection is smooth

Configure an IP address on the NIC connected to the client and the server to ensure that the IP address is in the same network segment as the IP address of the server interface GigabitEthernet1/0/0. Ping the IP address of the GigabitEthernet1/0/0 interface from the client. If the IP address can be pinged, the connection is smooth and physical line faults can be ruled out.

You can also enable DHCP debugging on the server to check whether the client's DHCPDISCOVER packet can be received.

DHCP troubleshooting Step 2. Check whether the configuration of the DHCP server is correct

The procedure is as follows:

A. Run the dhcp enable command to enable the DHCP service.

B. Execute the command display dhcp server tree all to check whether the global address pool exists and whether the IP address in the address pool and the IP address in the interface GigabitEthernet1/0/0 are in the same network segment.

◆ If the address pool does not exist, run the commands dhcp server ip-pool-name and command network ip-address [mask {mask | mask-length}] to create an address pool and configure the dynamically allocated ip address ranges in the address pool. If the client still cannot obtain the IP address, perform Step c.

◆ If the address pool exists but the IP address in the address pool is not in the same CIDR block as the IP address of interface GigabitEthernet1/0/0, modify the IP address in the address pool or the IP address of interface GigabitEthernet1/0/0, make the two in one CIDR block. If the client still cannot obtain the IP address, perform Step c.

◆ If the address pool exists and the IP address in the address pool is in the same CIDR block as the interface GigabitEthernet1/0/0, perform Step c.

C. execute the command dhcp select global {all | interface-type interface-number} in the System View or execute the command dhcp select global in the GigabitEthernet1/0/0 interface view, make sure that customers in GigabitEthernet1/0/0 get addresses from the global address pool. If the client still cannot obtain the IP address, perform step 3.

DHCP troubleshooting Step 3. check whether there are available IP addresses, expired IP addresses, or conflicting IP addresses in the address pool.

The following steps can be taken:

A. Execute the command display dhcp server free-ip to check whether there are available ip addresses in the global address pool. If you have any available addresses, contact Huawei technical support engineers.

B. If no address is available, run the command display dhcp server expired pool-name to check whether an expired IP address exists. If you have an expired IP address, contact the Technical Support Engineer of Huawei.

C. If no expired IP address exists, run the command display dhcp server conflict all to check whether there is a conflicting IP address. If so, check whether the probe Time Discover Time has exceeded 1 hour. In the implementation of NE80E/40E, if a conflicting IP address is found, the IP address can be re-allocated after one hour.

◆ If no conflicting IP addresses exist, the available IP addresses, expired IP addresses, and conflicting IP addresses in the address pool do not exist. This means that the IP addresses in the address pool are exhausted and you can create a new global address pool, the Network of the address pool overlaps with that of the previous address pool, and the Network segment is greater than that of the previous address pool.

◆ If a conflicting IP address exists and the detection time exceeds 1 hour, contact Huawei technical support engineers.

◆ If a conflicting IP address exists and the detection time does not exceed 1 hour, run the reset dhcp server conflict all command to release the conflicting IP address. If the client still cannot obtain the IP address, contact the Technical Support Engineer of Huawei.