Which port is an exception to the Port Lockdown function of Self-IPs if a device-group...

Self-IPs implement a security feature known asPort Lockdown, which limits which services are reachable on a Self-IP.

However, certain services required for BIG-IP device-to-device communication bypass Port Lockdown to ensure cluster and HA functionality.

TCP 4353

TCP port4353is used byDevice Service Clustering (DSC)for:

Device trust establishment

Configuration synchronization

Failover communication

Because BIG-IP devices must always be able to communicate for HA functions to remain operational, port 4353 isexempt from Port Lockdown rules.

Why the other options are incorrect

A. TCP 443

Not required for device trust or synchronization.

HTTPS access is fully controlled by Port Lockdown.

C. UDP 53

DNS traffic is not required for synchronization and has no exemption under Port Lockdown.