R0106-HP MSR Router Series Layer 3 - IP Services Configuration Guide(V7)

HP recommends that you make sure the primary subnet can be matched so the DHCP server turns to the

secondary subnets only when the matching primary subnet has no assignable IP addresses. If only a

secondary subnet is matched, the DHCP server does not select any IP address from other secondary

subnets when the matching secondary subnet has no assignable addresses.

NOTE:

To make sure address allocation functions correctly, keep the IP addresses used for dynamic allocation on

the subnet where the interface of the DHCP server or DHCP relay agent resides if possible.

IP address allocation sequence

The DHCP server selects an IP address for a client in the following sequence:

1. IP address statically bound to the client's MAC address or ID.

2. IP address that was ever assigned to the client.

3. IP address designated by the Option 50 field in the DHCP-DISCOVER message sent by the client.

Option 50 is the Requested IP Address option. The client uses this option to specify the wanted IP

address in a DHCP-DISCOVER message. The content of Option 50 is user defined.

4. First assignable IP address found in the way discussed in "DHCP address pool."

5. IP address that was a

onflict or passed its lease duration. If no IP address is assignable, the server

does not respond.

NOTE:

• If a client moves to another subnet, the DHCP server selects an IP address in the address pool matchin

the new subnet instead of assigning the IP address that was once assigned to the client.

• Conflicted IP addresses can be assi

ned to other DHCP clients only after the addresses are in conflict for

an hour.

DHCP server configuration task list

Tasks at a

lance

(Required.) Configuring an address pool on the DHCP server

(Required.) Enabling DHCP

(Required.) Enabling the DHCP server on an interface

(Optional.) Applying an address pool on an interface

(Optional.) Configuring IP address conflict detection

(Optional.) Enabling handling of Option 82

(Optional.) Configuring DHCP server compatibility

(Optional.) Setting the DSCP value for DHCP packets sent by the DHCP server