Network Pools

When the device is serving as a DHCP server, one or more pools of IP addresses must be defined, from which the device allocates IP addresses to DHCP clients. Each network pool contains a range of addresses that belong to a specific subnet. These addresses are allocated to various clients within that subnet.

When a client requests an IP address, the device as DHCP server allocates an IP address according to the following:

  • Directly Attached Client—The device allocates an address from the network pool whose subnet matches the subnet configured on the device’s IP interface from which the DHCP request was received.

    If the message arrived directly (not via DHCP Relay) the pool is a Local pool and belongs to one of IP subnets defined on the input layer 2 interface. In this case, the IP mask of the pool equals to the IP mask of the IP interface and the minimum and maximum IP addresses of the pool belong to the IP subnet.

  • Remote Client—The device takes an IP address from the network pool with the IP subnet that matches the IP address of the DHCP relay agent.

    If the message arrived via DHCP relay, the address used belongs to the IP subnet specified by minimum IP address and IP mask of the pool. That pool is a remote pool.

Up to 16 network pools can be defined.

To create a pool of IP addresses, and define their lease durations, follow these steps:

Procedure

Step 1

Click IPv4 Configuration > DHCP Server > Network Pools.

The previously defined network pools are displayed. These fields are described below in the Add page. The following field is displayed (but not in the Add page):

  • Number of Leased Addresses—Number of addresses in the pool that have been assigned (leased).

Step 2

Click Add to define a new network pool. Note that you either enter the Subnet IP Address and the Mask, or enter the Mask, the Address Pool Start and Address Pool End.

Step 3

Enter the fields:

  • Pool Name—Enter the pool name.

  • Subnet IP Address—Enter the subnet in which the network pool resides.

  • Mask—Enter one of following:

    • Network Mask—Check and enter the pool’s network mask.

    • Prefix Length—Check and enter the number of bits that comprise the address prefix.

  • Address Pool Start—Enter the first IP address in the range of the network pool.

  • Address Pool End—Enter the last IP address in the range of the network pool.

  • Lease Duration—Enter the amount of time a DHCP client can use an IP address from this pool. You can configure a lease duration of up to 49,710 days or an infinite duration.

    • Infinite—The duration of the lease is unlimited.

    • Days—The duration of the lease in number of days The ranges is 0–49,710 days.

    • Hours—The number of hours in the lease A days value must be supplied before an hours value can be added.

    • Minutes—The number of minutes in the lease A days value and an hours value must be added before a minutes value can be added.

  • Default Router IP Address (Option 3)—Select from the following:

    • Auto

    • Disable

    • User Defined - Enter the default router IP address

  • Domain Name Server IP Address (Option 6)—Select one of the devices DNS servers (if already configured) or select Other and enter the IP address of the DNS server available to the DHCP client.

  • Domain Name (Option 15)—Enter the domain name for a DHCP client.

  • NetBIOS WINS Server IP Address (Option 44)—Enter the NetBIOS WINS name server available to a DHCP client.

  • NetBIOS Node Type (Option 46)—Select how to resolve the NetBIOS name. Valid node types are:

    • Hybrid—A hybrid combination of b-node and p-node is used. When configured to use h-node, a computer always tries p-node first and uses b-node only if p-node fails. This is the default.

    • Mixed—A combination of b-node and p-node communications is used to register and resolve NetBIOS names. M-node first uses b-node; then, if necessary, p-node. M-node is typically not the best choice for larger networks because its preference for b-node. Broadcasts increase network traffic.

    • Peer-to-Peer—Point-to-point communications with a NetBIOS name server are used to register and resolve computer names to IP addresses.

    • Broadcast—IP Broadcast messages are used to register and resolve NetBIOS names to IP addresses.

  • SNTP Server IP Address (Option 4)—Select one of the device’s SNTP servers (if already configured) or select Other and enter the IP address of the time server for the DHCP client.

  • File Server IP Address (siaddr)—Enter the IP address of the TFTP/SCP server from which the configuration file is downloaded.

  • File Server Host Name (sname/Option 66)—Enter the name of the TFTP/SCP server.

  • Configuration File Name (file/Option 67)—Enter the name of the file that is used as a configuration file.

Step 4

Click Apply. The Running Configuration file is updated.