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Configuring Address Pools
You must configure IP address pools for each IP interface that will provide
addresses to attached clients via the DHCP server.
Command Usage
• First configure address pools for the network interfaces. Then you can manually
bind an address to a specific client if required. However, note that any static host
address must fall within the range of an existing network address pool. You can
configure up to 8 network address pools, and up to 32 manually bound host
address pools (i.e., one address per host pool).
• When a client request is received, the switch first checks for a network address
pool matching the gateway where the request originated (i.e., if the request was
forwarded by a relay server). If there is no gateway in the client request (i.e., the
request was not forwarded by a relay server), the switch searches for a network
pool matching the interface through which the client request was received. It then
searches for a manually configured host address that falls within the matching
network pool. If no manually configured host address is found, it assigns an
address from the matching network address pool. However, if no matching address
pool is found the request is ignored.
• When searching for a manual binding, the switch compares the client identifier and
then the hardware address for DHCP clients. Since BOOTP clients cannot transmit
a client identifier, you must configure a hardware address for this host type. If no
manual binding has been specified for a host entry with a hardware address or
client identifier, the switch will assign an address from the first matching network
pool.
• If the subnet mask is not specified for network or host address pools, the class A,
B, or C natural mask is used (see page 20-5). The DHCP server assumes that all
host addresses are available. You can exclude subsets of the address space by
using the IP Excluded Address field on the DHCP Server General configuration
page.
Command Attributes
Creating a New Address Pool
• Pool Name – A string or integer. (Range: 1-8 characters)
• Type – Shows is address pool type is Network or Host.
• IP Address – The IP address upon which the pool is based.
• Mask – Shows the network (or subnet) and the host portion of the address pool.
• Active Pool – The addresses provided by this pool, including those specified by
the IP address and network mask, but minus those excluded on the DHCP server’s
General Configuration page.
17-4
CLI
– This example enables the DHCP and sets an excluded address range.
Console(config)#service dhcp
Console(config)#ip dhcp excluded-address 10.1.0.250 10.1.0.254
Console#
39-5
3
9
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6
Dynamic Host Configuration Protocol
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