F5 BIG-IP load balancer certificate automation

Automate the complete certificate lifecycle at the F5 TLS termination point and on backend web servers while keeping application traffic encrypted through the DMZ.

In this architecture, an F5 BIG-IP LTM terminates the client-side TLS session at the virtual IP (VIP) and establishes a separate TLS connection to the backend web servers. As a result, certificates must be managed at two layers: the F5 for browser-facing TLS and the backend web servers for the encrypted server-side connection. DigiCert Trust Lifecycle Manager can coordinate both layers with purpose-built automation components. DigiCert sensors manage supported F5 appliances, while DigiCert agents manage certificates on supported backend web servers.

TLS termination on a single load balancer

The DigiCert sensor initiates outbound HTTPS connectivity to Trust Lifecycle Manager and uses an internal management connection to the F5. End-user HTTPS traffic goes through the firewall to the F5 VIP, where the client-side TLS session terminates. The F5 then initiates a separate HTTPS connection to backend web servers.

Why this scenario matters

F5 BIG-IP LTM appliances often sit in front of multiple applications and virtual IPs, making certificate health critical across the entire application path. In a TLS re-encryption architecture, organizations must manage certificates at two connection points: the public-facing TLS session between users and the F5, and the backend TLS session between the F5 and the web servers.

If the F5 certificate expires or is deployed incorrectly, users may be unable to establish the public TLS session. But even when the F5 certificate is valid, an expired, untrusted, or misconfigured backend certificate can still break the F5-to-web-server connection.

As a result, the key design question is not just whether the F5 certificate can be renewed. Organizations must also account for backend certificate discovery and automation, F5 Client SSL and Server SSL configuration, high-availability behavior, trust chains, hostname or SNI requirements, and the network access required by each automation component.

How DigiCert fits

Sensor-based F5 automation

A DigiCert sensor runs on a separate host and manages the F5 connector. No DigiCert agent is installed on the F5 appliance.

Agent-based backend web-server automation

DigiCert agents installed on supported backend servers can discover, renew, and deploy the certificates used for the F5-to-server TLS connection.

Separate certificate lifecycles

The F5 certificate secures the browser-facing TLS session. Backend certificates secure the separate server-side TLS session. TLM can manage both without treating them as a single certificate endpoint.

Central visibility and policy

TLM centralizes inventory, automation profiles, lifecycle-event status, and deployment verification so teams can distinguish issuance from installation.

At a glance

Environment: a supported F5 BIG-IP LTM appliance receives inbound HTTPS at the VIP, terminates the client-side TLS session, and then establishes a separate HTTPS connection to backend web servers. Both the F5 and backend web servers use certificates.
DigiCert deployment model: Trust Lifecycle Manager SaaS with an on-premises DigiCert sensor for the F5 connector, plus a DigiCert agent on each supported backend web server whose certificates are managed by TLM. Sensors and agents use outbound HTTPS connectivity to TLM.
Typical validation approach: validation depends on the certificate type and issuing CA. Public certificates may require automated domain control validation; backend certificates can use an appropriate public or private trust model based on the F5 Server SSL configuration and organizational policy.
What to verify before deployment: supported F5 and web-server versions, sensor and agent system requirements, F5 management connectivity, backend agent connectivity, F5 Client SSL and Server SSL behavior, trust chains, SNI/hostname requirements, key storage, HA design, DNS/DCV needs, and certificate automation profiles.

Technical implementation details

This scenario contains two certificate-management paths. The F5 connector and DigiCert sensor manage certificates presented by the F5 VIP. DigiCert agents can manage certificates installed on supported backend web servers.

The F5-to-backend HTTPS connection also depends on the F5 Server SSL configuration and the trust relationship for the backend certificate. Exact F5 versions, management ports, sensor and agent hosts, proxy settings, credentials, key-storage options, DNS integrations, certificate profiles, SNI behavior, and HA settings can vary by deployment. Confirm current prerequisites and procedures in DigiCert and F5 documentation before implementation.

F5 BIG-IP LTM integration guide — review the supported F5 connector architecture, sensor requirements, discovery, and certificate automation workflow for the load-balancer certificate layer.
Managed automation solution — review DigiCert agent-based certificate automation for supported IIS, Apache, NGINX, IBM HTTP Server, and Tomcat systems used as backend web servers.
Agent system/network requirements — verify outbound HTTPS connectivity, supported host operating systems, proxy options, and the requirement to run agents on appropriate systems.
Sensor and network connectivity requirements — verify outbound HTTPS connectivity, supported host operating systems, proxy options, and the requirement to run sensors on appropriate systems.
DNS integrations for domain validation — understand when TLM can use DNS integrations to automate domain validation for public certificate lifecycle events at either certificate layer.

Frequently asked questions

How does DigiCert TLM manage certificates on the F5 and on the backend web servers?

TLM uses different automation components for the two certificate layers. A DigiCert sensor on a separate host manages the F5 BIG-IP LTM connector and communicates with the F5 management interface. For supported backend web servers, a DigiCert agent is installed on each server system that hosts certificates to be discovered and managed. Both sensors and agents use outbound connectivity to TLM rather than requiring inbound management access from the DigiCert cloud.

Does the F5 management interface or a backend web server need to be exposed to DigiCert TLM on the internet?

No, the DigiCert sensor uses outbound HTTPS to communicate with Trust Lifecycle Manager and needs internal network access to the F5 management interface. DigiCert agents on supported backend web servers also use outbound HTTPS to synchronize with TLM. The F5 management interface and backend management interfaces do not need to be publicly exposed for TLM SaaS to initiate inbound management sessions.

Do the F5 and backend web servers use the same certificate?

They should be treated as separate certificate endpoints because they participate in separate TLS sessions. The F5 presents a certificate to external clients on the browser-facing connection, while each backend web server presents a certificate to the F5 on the server-side connection. The certificate authority, certificate profile, names, validity period, and key-storage requirements for those two layers can differ based on the organization's architecture and trust model.

Do backend web-server certificates need to be publicly trusted?

Not necessarily. The backend connection is inside the organization's architecture, so the appropriate trust model depends on how the F5 Server SSL profile validates the backend server. Organizations can use public or private certificates where supported, provided the F5 trusts the issuing chain and the certificate identity and TLS settings match the intended backend connection. Verify the F5 Server SSL configuration and certificate policy for your environment.

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