3Com S7902E, Руководство по настройке

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If a DHCP relay agent exists between the DHCP server and client, the DHCP server, regardless of
whether the subaddress keyword is used, will select an IP address from the address pool containing
the primary IP address of the DHCP relay agent’s interface (connected to the client) for a requesting
client.
When the DHCP server and client are on the same subnet:
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With the keyword subaddress specified, the DHCP server will assign an IP address from the
address pool containing the secondary IP address of the server interface (connected to the client);
if the interface has multiple secondary IP addresses, the address pool containing the first
secondary IP address is selected. If the interface has no secondary IP addresses, the server is
unable to assign an IP address to the client.
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Without the keyword subaddress specified, the DHCP server will assign an IP address from the
address pool containing the primary IP address of the server interface (connected to the client).
Applying an Extended Address Pool on an Interface
After you create an extended address pool and apply it on an interface, the DHCP server, upon
receiving a client's request on the interface, will assign an IP address from this address pool to the client.
If no IP address is available in this address pool, address allocation fails, and the DHCP server will not
assign an IP address from other address pools.
Follow these steps to apply an extended address pool on an interface:
To do… Use the command… Remarks
Enter system view
system-view
—
Enter interface view
interface interface-type
interface-number
—
Apply an extended address
pool on the interface dhcp server apply ip-pool
pool-name
Optional
By default, the DHCP server has
no extended address pool applied
on its interface, and assigns an IP
address from a common address
pool to a requesting client.
Only an extended address pool can be applied on the interface. The address pool to be referenced
must already exist.
Configuring the DHCP Server Security Functions
This configuration is necessary to secure DHCP services on the DHCP server.