TLS Versions and Cipher Suites for Load Balancer Reference

Published April 5, 2023 | Last modified September 3, 2026

Objective

This document provides information on the TLS versions and cipher suites supported for the HTTP load balancers and associated origin pools.

The TLS versions and cipher suites mentioned in this guide are supported for the following entities of F5® Distributed Cloud Services:

HTTPS Load Balancer with Automatic Certificate
HTTPS Load Balancer with Custom Certificate/Bring Your Own Certificate (BYOC)
Origin Pool (origin servers that use TLS)

TLS Versions and Cipher Suites

F5 Distributed Cloud Services provide predefined security levels that apply minimum and maximum TLS versions and associated cipher suites for the levels. You can select the security levels or apply custom TLS security settings in F5® Distributed Cloud Console.

The following table lists the TLS security levels and associated cipher suites:

Security Level	TLS Versions	Cipher Suites	Details
Default	Minimum TLS 1.2 Maximum TLS 1.3	`TLS_AES_128_GCM_SHA256` `TLS_AES_256_GCM_SHA384` `TLS_CHACHA20_POLY1305_SHA256` `TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256` `TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384` `TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256` `TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256` `TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384` `TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256`	Applied by default. This is also the high security level.
Medium	Minimum TLS 1.0 Maximum TLS 1.3	Cipher suites of default level `TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA` `TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA` `TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA` `TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA`	Selecting medium security level also gets the cipher suites of default or high security levels.
Low	Minimum TLS 1.0 Maximum TLS 1.3	Cipher suites of default and medium levels `TLS_RSA_WITH_AES_128_CBC_SHA` `TLS_RSA_WITH_AES_128_GCM_SHA256` `TLS_RSA_WITH_AES_256_CBC_SHA` `TLS_RSA_WITH_AES_256_GCM_SHA384`	Selecting low security level also gets the cipher suites of default and medium levels.

Note: The HTTPS load balancer with automatic certificate uses default security level by default.
If TLSv1.3 is selected as either the Minimum TLS version or Maximum TLS version, it is mandatory you add the following TLS 1.3 cipher suites:

TLS_AES_128_GCM_SHA256

TLS_AES_256_GCM_SHA384

TLS_CHACHA20_POLY1305_SHA256

TLS automatic certificate renewal failure alerts and troubleshooting

In case of TLS certificate auto-renewal failure or expiry, the following alerts are triggered:

TLSAutomaticCertificateRenewalFailure: This is a major alert and triggered when renewal attempts are failing when the expiry date is within the period of 15 - 28 days.
TLSAutomaticCertificateRenewalStillFailing: This is a critical alert triggered when renewal attempts are failing when the expiry date is within 15 days.
TLSAutomaticCertificateExpired: This is a critical alert triggered when the certificate is expired.

Do the following to troubleshoot automatic certificate renewal failures:

Step 1: Verify that root domain NS and SOA records are configured correctly.

Enter the following commands:

dig NS <root-domain>

dig SOA <root-domain>

Step 2: Verify root domain CAA record.

If there is any CAA record created for a root domain, then you must either add additional record to include letsencrypt.org, or remove every existing CAA record.

Enter the following command:

dig CAA <root-domain>

Step 3: Verify delegated domains.

In case of delegated domains, do the following:

Verify in Console that domain object is in publish state and F5 Distributed Cloud NS servers are listed for the domain.
Verify NS record created for the delegated domain in the root domain registrar. The NS record should point to F5 Distributed Cloud NS servers. Verify using the following command (output returns F5 Distributed Cloud DNS servers):

dig NS <delegated-domain>

Step 4: Verify non-delegated domains.

Verify that ACME challenge CNAME records are created in the domain registrar for all domains, and they point to the values provided by F5 Distributed Cloud Services.

Use the following command to verify:

dig CNAME _acme-challenge.<non-delegated-domain>

Output for the command above returns CNAME records that match load balancer DNS records.

TLS custom certificate expiry alerts and troubleshooting

In case of TLS custom certificate expiry, the following alerts are triggered:

TLSCustomCertificateExpiring: This is a major alert and triggered when the expiry date is within the period of 15 - 28 days.
TLSCustomCertificateExpiringSoon: This is a critical alert triggered when the expiry date is within 15 days.
TLSCustomCertificateExpired: This is a critical alert triggered when the certificate is expired.

As this is a user-managed custom certificate, you must update the certificate via Distributed Cloud Console or API to avoid any downtime.

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