H3C Technologies H3C S3100 Series Switches - Manual (Page 528)

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If you use the inheriting relation of parent and child address pools, make sure that the number of the
assigned IP addresses does not exceed the number of the IP addresses in the child address pool;
otherwise extra IP addresses will be obtained from the parent address pool, and the attributes (for
example, gateway) also are based on the configuration of the parent address pool.
For example, in the network to which VLAN-interface 1 is connected, if multiple clients apply for IP
addresses, the child address pool 10.1.1.0/25 assigns IP addresses first. When the IP addresses in the
child address pool have been assigned, if other clients need IP addresses, the IP addresses will be
assigned from the parent address pool 10.1.1.0/24 and the attributes will be based on the configuration
of the parent address pool.
For this example, the number of clients applying for IP addresses from VLAN-interface 1 is
recommended to be less than or equal to 122 and the number of clients applying for IP addresses from
VLAN-interface 2 is recommended to be less than or equal to 124.
Network diagram
Figure 2-2 Network diagram for DHCP configuration
Configuration procedure
1) Configure a VLAN and add a port in this VLAN, and then configure the IP address of the VLAN
interface (omitted).
2) Configure DHCP service.
# Enable DHCP.
system-view
[SwitchA] dhcp enable
# Configure the IP addresses that are not dynamically assigned. (That is, the IP addresses of the DNS
server, WINS server, and gateways.)
[SwitchA] dhcp server forbidden-ip 10.1.1.2
[SwitchA] dhcp server forbidden-ip 10.1.1.4
[SwitchA] dhcp server forbidden-ip 10.1.1.126
[SwitchA] dhcp server forbidden-ip 10.1.1.254