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Manual Chapter: Configuring the BIG-IP System for DHCP Renewal
Manual Chapter
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Overview: Renewing IP addresses for DHCP clients

You can configure the BIG-IP system to manage DHCP renewal requests and responses.

Before configuring the BIG-IP system to manage DHCP renewal requests and responses, it is helpful to understand some BIG-IP system terminology:

BIG-IP object type Definition
BIG-IP pool member A DHCP relay target (such as a DHCP server or BOOTP server). This is the dynamic address server to which the BIG-IP system forwards unicast requests.
BIG-IP virtual server A BIG-IP system address on the listening VLAN
BIG-IP VLAN assigned to a virtual server A listening VLAN, controlled on a per-virtual server basis

About DHCP renewal

You can configure the BIG-IP system to act as a DHCP renewal system. A common reason to configure the BIG-IP system as a renewal system is when the DHCP servers reside on a different subnet than that of the client systems, and the BIG-IP system is also configured as a DHCP relay agent. As a DHCP renewal system, the BIG-IP system manages the renewal of client IP addresses by DHCP servers before the addresses expire.

During the renewal process, a DHCP client sends a renewal request, which is passed through a BIG-IP Forwarding IP type of virtual server directly to the specific DHCP server that issued the initial client IP address. The DHCP server then sends a response to renew the lease for the client's IP address.

In the example shown in the illustration, a DHCP client sends a renewal message to the same BIG-IP system that initially acted as the DHCP relay agent. This renewal request is forwarded through a BIG-IP renewal virtual server directly to DHCP server 1. DHCP server 1 then provides a response to renew the lease for the client's IP address.

sample DHCP renewal system configuration A sample DHCP renewal system configuration

Task summary

You configure a BIG-IP system to act as a Dynamic Host Configuration Protocol (DHCP) relay system by creating a virtual server that specifically forwards DHCP renewal requests to the appropriate DHCP server.

Task list

Creating a DHCP renewal virtual server

A Dynamic Host Configuration Protocol (DHCP) renewal virtual server forwards a DHCP request message from a DHCP client directly to a DHCP server, to automatically renew an IP address before it expires.
  1. On the Main tab, click Local Traffic > Virtual Servers. The Virtual Server List screen opens.
  2. Click the Create button. The New Virtual Server screen opens.
  3. In the Name field, type a unique name for the virtual server.
  4. Optional: Type a description for the virtual server.
  5. From the Type list, select Forwarding (IP).
  6. For a Destination type, select Host, and type the DHCP server IP address in the Address field.
    Tip: If you have multiple DHCP servers, type 0.0.0.0 in the Address field.
  7. In the Service Port field, type 67 (IPv4) or 547 (IPv6).
  8. From the Protocol list, select UDP.
  9. From the VLAN and Tunnel Traffic list, select the VLANs on the same network as the DHCP clients.
  10. Click Finished.
The BIG-IP system is now configured with a virtual server that can forward DHCP renewal requests directly to the appropriate DHCP server.

Implementation result

The BIG-IP system is configured to forward DHCP client renewal requests to appropriate DHCP servers that reside on a different subnet than the client systems. The BIG-IP also forwards the DHCP server responses back to the client systems, therefore ensuring that client IP addresses do not expire.

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