Manual Chapter : Configuring the BIG-IP System for DHCP Renewal

Applies To:

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BIG-IP DNS

  • 15.0.1, 15.0.0

BIG-IP PEM

  • 15.0.1, 15.0.0

BIG-IP AFM

  • 15.0.1, 15.0.0

BIG-IP Analytics

  • 15.0.1, 15.0.0

BIG-IP ASM

  • 15.0.1, 15.0.0

BIG-IP AAM

  • 15.0.1, 15.0.0

BIG-IP APM

  • 15.0.1, 15.0.0

BIG-IP LTM

  • 15.0.1, 15.0.0
Manual Chapter

Configuring the BIG-IP System for DHCP Renewal

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.
A sample DHCP renewal system configuration
sample DHCP renewal system configuration

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
    Create
    .
    The New Virtual Server screen opens.
  3. In the
    Name
    field, type a unique name for the virtual server.
  4. Type a description for the virtual server.
  5. From the
    Type
    list, select
    Forwarding (IP)
    .
  6. For a host, in the
    Destination Address
    field, type an IPv4 or IPv6 address in CIDR format to allow all traffic to be translated.
    The supported format is address/prefix, where the prefix length is in bits. For example, an IPv4 address/prefix is
    0.0.0.0/0
    , and an IPv6 address/prefix is
    ::/0
    .
  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.