F5CAB1 Exam Dumps - F5-CA Questions and Answers

Port Lockdown controls which ports and protocols aSelf IPwill respond to.

However, certain traffic types bypass Port Lockdown for BIG-IP functionality and routing integrity.

The three types that areNOT affectedby Port Lockdown are:

1. Defined Virtual Server Traffic

Traffic destined to a Self IP that matches aconfigured virtual serveris always accepted by the BIG-IP, regardless of Port Lockdown settings.

This ensures that traffic processing does not break when administrators restrict Self-IP ports.

2. ICMP (Internet Control Message Protocol)

ICMP (such as ping, traceroute responses, etc.) always passes through a Self IP even when Port Lockdown is set to:

Allow Default

Allow None

Allow Custom

F5 allows ICMP for reachability and diagnostic purposes independent of Port Lockdown rules.

3. Centralized Management Infrastructure (CMI)

CMI includes the internal HA services used for:

Device Trust

ConfigSync

Failover

Mirroring

These essential HA communications bypass Port Lockdown to prevent accidental cluster failure.

The well-known port for this traffic isTCP 4353, which is always permitted.

Why the other options are incorrect:

Option A:SSHisrestricted by Port Lockdown unless explicitly allowed.

Option B:Same issue — SSH does not bypass Port Lockdown.

OnlyDefined VS Traffic,ICMP, andCMIbypass Port Lockdown.

The screenshot shown is from theUser Administrationsection of the BIG-IP GUI.

This section controls:

Root and Admin passwords

SSH Access

SSH IP Allow settings

However,it does not contain any controls for restricting access to the WebUI (TMUI).

BIG-IP does not provide TMUI access restrictions from this part of the GUI.

Access to the web-based Configuration Utility is controlled by thehttpd allow list, configured through TMSH:

tmsh modify /sys httpd allow { }

This setting is not displayed in the User Administration panel, and in many BIG-IP versions, the httpd allow list isonly configurable from the CLI, not the GUI.

Therefore, the administrator cannot find the setting in the screen shown because:

TMUI access restriction isnotlocated in this GUI section

It must be configured usingtmshunder/sys httpd allow

This is whyOption Ais correct.

From the exhibit, the administrator performs the following actions:

Displays the current SSH allow configuration:

tmsh list sys sshd allow

allow { ALL }

Replaces the existing SSH allow list with a specific subnet:

tmsh modify sys sshd allow replace-all-with { 10.0.0.0/24 }

Confirms the updated configuration:

tmsh list sys sshd allow

allow { 10.0.0.0/24 }

This configuration restricts SSH access to only hosts that fall within the10.0.0.0/24network.

Evaluation of the options

A. 10.0.0.100

This address is within the 10.0.0.0/24 subnet and is a valid host address, so SSH access is permitted.

B. 10.0.0.254

This address is also within the 10.0.0.0/24 subnet and is a valid host address, so SSH access is permitted.

C. 10.0.0.256

This is not a valid IP address because an IPv4 octet cannot exceed 255.

D. 100.0.1.10

This address is outside the configured 10.0.0.0/24 subnet and will not be allowed.

E. 100.0.0.10

This address is also outside the configured subnet and will not be allowed.