DHCP clients fail to obtain IP addresses from the DHCP server on the AR

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The causes that DHCP clients fail to obtain IP addresses from the DHCP server are as follows:
- The configuration is incorrect.
- There is no allocable IP address in the DHCP address pool.
- STP is enabled on upper-level access devices of some diskless workstations. For details on troubleshooting and solutions, see AR150&AR160&AR200&AR510&AR1200&AR2200&AR3200 FAQ.


About the AR ClientExceptions occurs when the IP address is obtained. For details, see the Revelations of Troublesolving on the right page.

Other related questions:
DHCP client cannot obtain a correct IP address
The request packets (DHCP discover) are broadcast by the DHCP clients. If multiple DHCP servers are located on the same subnet (for example, bogus DHCP server), the clients may obtain IP addresses from a bogus DHCP server. To address this problem, configure DHCP snooping. Then clients can receive DHCP packets from only the trusted DHCP server. Perform the following configuration: [Huawei] dhcp enable [Huawei] dhcp snooping enable [Huawei] interface gigabitethernet 1/0/1 //Enter the view of the interface connected to the DHCP client. [Huawei-GigabitEthernet1/0/1] dhcp snooping enable [Huawei-GigabitEthernet1/0/1] quit [Huawei] interface gigabitethernet 1/0/2 [Huawei-GigabitEthernet1/0/2] dhcp snooping trusted //Configure the interface of the DHCP server as the trusted interface. [Huawei-GigabitEthernet1/0/2] quit Note: - When you configure DHCP snooping on a Layer 2 access device, steps 1, 2, and 3 are mandatory and must be performed in the following sequence. - When you configure DHCP snooping on a DHCP relay agent, only steps 1 and 2 are required.

Failure to obtain IP addresses from DHCP server
For S series switches (except S1700 switches), a client may fail to obtain an IP address from the DHCP server due to the following: - Incorrect configuration - No available IP address in the address pool - STP enabled on the upper-layer access device of diskless workstations For the fault locating and troubleshooting procedure, see the section "A Client Fails to Obtain an IP Address from a DHCP Server" in Configuration Guide �?IP Service.

An AR used as a DHCP client cannot obtain an IP address
When the configuration is correct, you can shorten the IP address lease. If the IP address lease is long, after addresses in the address pool are allocated, the address that has been allocated to a client is no longer used and cannot be released. As a result, other DHCP clients cannot obtain the IP address.

How does an AR used as the DHCP server allocate IP addresses to many DHCP clients
When an AR functions as a DHCP server, you can enlarge the address pool range and shorten the lease of IP addresses to allow DHCP clients to quickly connect to and disconnect from the network.

An AP fails to obtain an IP address through DHCP
Perform the following steps to locate the fault: 1. Check whether the AP is configured to obtain an IP address through DHCP. 2. Check whether the Layer 2 link between the AP and DHCP server is working properly. 3. Run the display ip pool name ip-pool-name used command on the DHCP server to check whether the AP has obtained an IP address.

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