Creating an Address Pool

Context

Create an interface address pool for IP address allocation to clients on the same network segment as the DHCP server's interface, or create a global address pool for IP address allocation to all clients connected to the DHCP server.

After an address pool is created, the following IP addresses on the network segment cannot be automatically assigned:

Network address (with host bits of all 0s)
Broadcast address (with host bits of all 1s)
Gateway address for DHCP clients (configured in (Optional) Configuring a Gateway Address for Clients)

Procedure

Create an interface address pool.
1. Enter the system view.
```
system-view
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
  Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731S-H, S5731-S, S5731S-S, S6720-HI, S5732-H, S6730-H, S6730S-H, S6730-S, S6730S-S, S6720-EI, and S6720S-EI support sub-interfaces.
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
  
  Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
4. Configure an IP address for the interface.
```
ip address ip-address { mask | mask-length }
```
  The IP address segment of the interface is the interface address pool. The interface address mask cannot be set to 31; otherwise, the interface address pool may fail to be configured.
Create a global address pool.
1. Enter the system view.
```
system-view 
```
2. Create a global address pool and enter the global address pool view.
```
ip pool ip-pool-name
```
  By default, no global address pool is created on the device.
  
  The parameter ip-pool-name uniquely specifies the name of an address pool. For example, create a global address pool named global_f1 for employees on the first floor as follows:
  
  [HUAWEI] ip pool global_f1
3. Specify the range of IP addresses to be dynamically allocated from the address pool.
```
network ip-address [ mask { mask | mask-length } ]
```
  By default, the range of IP addresses that can be allocated dynamically to clients is not specified.
  
  An address pool can be configured with only one IP address segment. The IP address range is determined by the mask length.
  
  When specifying the IP address range, ensure that IP addresses within the range are on the same network segment as the interface IP address of the DHCP server or DHCP relay agent to avoid incorrect IP address allocation.
  
  When configuring an address pool, ensure that IP addresses on the network address segment must be class A, B, or C IP addresses, and the mask cannot be set to 0, 1, 31, or 32.
4. (Optional) Configure a VPN instance for the address pool.
```
vpn-instance vpn-instance-name
```
  By default, no VPN instance is configured for an address pool.
  
  In most cases, IP addresses in an address pool are allocated to clients on only one network segment to prevent IP address conflicts. In a BGP/MPLS IP VPN scenario, different VPNs use IP addresses on the same network segment. If clients in different VPNs apply to the same DHCP server for IP addresses, perform this step to use the same address pool to allocate IP addresses on the same network segment to the clients.