A Client Fails to Obtain an IP Address

Possible Cause 1	DHCP is disabled.
Verification	Check whether DHCP is enabled. Enter the user view and run: display current-configuration \| include dhcp enable If the command output is empty, DHCP is disabled.
Solution	Enable DHCP. Enter the system view and run: dhcp enable By default, DHCP is disabled in the system.

Possible Cause 2	The configuration is incorrect.
Verification	On the DHCP server: Check whether the address pool and client are on the same network segment and whether the configuration is correct. Run: display ip pool If a DHCP relay agent is deployed, check whether a route to the network segment of the client is configured on the DHCP server. On the DHCP relay agent: Check whether the DHCP relay agent is correctly configured. Run: display dhcp relay In the view of the interface connected to the client, check whether DHCP relay is enabled on the interface. Run: display this
Solution	Modify the configurations on the DHCP server and, if deployed, DHCP relay agents. For details, see Configuring a DHCP Server and Configuring a DHCP Relay Agent.

Possible Cause 2

The configuration is incorrect.

Verification

On the DHCP server:
- Check whether the address pool and client are on the same network segment and whether the configuration is correct. Run:
```
display ip pool
```
- If a DHCP relay agent is deployed, check whether a route to the network segment of the client is configured on the DHCP server.
On the DHCP relay agent:
- Check whether the DHCP relay agent is correctly configured. Run:
```
display dhcp relay
```
- In the view of the interface connected to the client, check whether DHCP relay is enabled on the interface. Run:
```
display this
```

Solution

Modify the configurations on the DHCP server and, if deployed, DHCP relay agents. For details, see Configuring a DHCP Server and Configuring a DHCP Relay Agent.

Possible Cause 3	The address pool has no available IP addresses.
Verification	Check whether there are IP addresses available in the address pool. Run: display ip pool The Idle(Expired) field displays the number of idle IP addresses in the address pool.
Solution	If the number of DHCP clients is greater than the number of available IP addresses in the address pool, increase the range of IP addresses in the address pool. For an interface address pool, run: ip address ip-address { mask \| mask-length } For a global address pool, run: network ip-address [ mask { mask \| mask-length } ] If the number of DHCP clients is less than the number of available IP addresses in the address pool, reduce the lease period and ensure that the DHCP server reclaims unused IP addresses. For details, see (Optional) Configuring Automatic Reclamation of Conflicting IP Addresses.

Possible Cause 3

The address pool has no available IP addresses.

Verification

Check whether there are IP addresses available in the address pool. Run:

display ip pool

The Idle(Expired) field displays the number of idle IP addresses in the address pool.

Solution

If the number of DHCP clients is greater than the number of available IP addresses in the address pool, increase the range of IP addresses in the address pool.
- For an interface address pool, run:
```
ip address ip-address { mask | mask-length }
```
- For a global address pool, run:
```
network ip-address [ mask { mask | mask-length } ]
```
If the number of DHCP clients is less than the number of available IP addresses in the address pool, reduce the lease period and ensure that the DHCP server reclaims unused IP addresses. For details, see (Optional) Configuring Automatic Reclamation of Conflicting IP Addresses.

Possible Cause 4	The Spanning Tree Protocol (STP) is enabled on a diskless workstation functioning as a DHCP client.
Verification	Check whether STP is enabled. Run: display stp
Solution	Disable STP on the diskless workstations. The timeout period of DHCP Discover messages sent from clients is shorter than the STP convergence time, and therefore the DHCP server cannot receive DHCP Discover messages or allocate IP addresses to the diskless workstations. Run: undo stp enable

Possible Cause 5	The IP address is manually configured for another host on the network. This causes an IP address conflict because the DHCP server does not exclude manually configured IP addresses from the address pool.
Verification	Disable the network adapter of the client or disconnect the network cable. Then, from another connected host, ping the conflicting IP address. If you can ping the IP address, it is manually configured.
Solution	Exclude the conflicting IP address from the address pool. For an interface address pool, run: dhcp server excluded-ip-address For a global address pool, run: excluded-ip-address Then, on the client, release the IP address and apply for a new one. Change the host's manually configured IP address. NOTE: IP address conflict detection can be configured on the DHCP server to prevent conflicts. For details, see (Optional) Configuring IP Address Conflict Detection.

Possible Cause 5

The IP address is manually configured for another host on the network. This causes an IP address conflict because the DHCP server does not exclude manually configured IP addresses from the address pool.

Verification

Disable the network adapter of the client or disconnect the network cable. Then, from another connected host, ping the conflicting IP address. If you can ping the IP address, it is manually configured.

Solution

Exclude the conflicting IP address from the address pool.
- For an interface address pool, run:
```
dhcp server excluded-ip-address
```
- For a global address pool, run:
```
excluded-ip-address
```
Then, on the client, release the IP address and apply for a new one.
Change the host's manually configured IP address.

NOTE:

IP address conflict detection can be configured on the DHCP server to prevent conflicts. For details, see (Optional) Configuring IP Address Conflict Detection.