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F5 Networks F5CAB1 Exam - Topic 3 Question 2 Discussion

Posted by Paz on Nov 20, 2025 at 11:38 PM

Which one of the following is a port and protocol combination allowed by the Allow Default setting for Port Lockdown?

Suggested Answer: C

Port Lockdown controls which ports and protocols a Self IP will respond to.

The Allow Default setting permits only a predefined set of BIG-IP internal and required service ports.

The Allow Default list includes:

TCP 443 HTTPS (Management/TMUI access via Self-IP)

TCP 4353 CMI (device sync)

TCP/UDP ports related to HA communication

Other essential internal F5 ports

Why TCP 443 is correct:

It is one of the officially allowed ports under Allow Default.

It enables HTTPS/TMUI access through a Self IP.

Why the other options are incorrect:

A . TCP 80 (HTTP)

Not allowed under Allow Default

HTTP via Self-IP is blocked unless placed under Allow Custom

B . UDP 8443

Not an F5 default service

Not part of the Allow Default ports


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30 comments · newest first
BO
Bobbye 6 months ago
Still, TCP 443 is the safest bet for default settings.
RE
Refugia 6 months ago
True, but UDP 8443 could be valid for some apps.
KA
Kati 7 months ago
But TCP 443 is more secure, right? Makes sense for lockdown.
WH
Whitney 7 months ago
I’m leaning towards TCP 80. It’s widely used too.
RO
Roosevelt 7 months ago
Wait, are we sure about this? Sounds off!
RO
Rosalyn 7 months ago
Yeah, TCP 443 is the secure one, right?
GE
Georgene 7 months ago
Pretty sure TCP 80 is standard for web traffic.
LE
Leigha 8 months ago
I thought UDP 8443 was allowed too?
MA
Malcolm 8 months ago
TCP 443 for the win! Gotta love those default settings.
GI
Giovanna 8 months ago
Haha, I bet the exam writers had a field day coming up with these tricky options.
NA
Nada 8 months ago
TCP 443 is the way to go. I remember that from my networking classes.
VA
Valentine 9 months ago
I always get these port and protocol questions mixed up. TCP 443 sounds about right.
CH
Chuck 9 months ago
C) TCP 443 is the correct answer.
EU
Eura 9 months ago
I believe TCP 443 is often used for HTTPS, so it might be the right answer, but I need to double-check my notes.
LI
Lizbeth 9 months ago
I'm a bit confused about UDP 8443; I don't recall seeing that in the default settings during my studies.
SH
Sherell 9 months ago
I remember practicing a question about port lockdowns, and I feel like TCP 443 was mentioned as a secure option.
RO
Ronna 10 months ago
Okay, I've got a strategy here. TCP 80 is for regular web traffic, UDP 8443 sounds a bit unusual, so I'm going to go with C) TCP 443 since that's the standard port for HTTPS.
VI
Vi 10 months ago
Ugh, I hate networking questions. There's just so much to remember with all these different ports and protocols. I'm going to have to guess on this one.
AN
Andra 10 months ago
I'm pretty confident I know the answer to this one. The "Allow Default" setting is all about the standard, commonly used ports and protocols, so I'd say C) TCP 443 is the right choice.
IR
Irma 10 months ago
Agreed, TCP 443 is standard for secure web traffic.
LE
Leontine 10 months ago
I think it's TCP 443. It's common for HTTPS.
HA
Hannah 10 months ago
TCP 443 is definitely a common one.
MA
Maybelle 11 months ago
I think TCP 80 is a common one for web traffic, but I'm not entirely sure if it's included in the default settings for Port Lockdown.
LA
Lanie 11 months ago
Okay, let's think this through. The question is asking about the "Allow Default" setting, so I'm guessing one of these options is the default allowed port and protocol. I'll have to weigh the pros and cons of each choice.
LE
Lennie 11 months ago
Hmm, I think I remember learning about port lockdown in class, but I'm a bit fuzzy on the details. I'll need to review my notes to be sure.
DE
Denise 6 months ago
↳ replying to Lennie
Definitely worth reviewing those notes!
RO
Roslyn 6 months ago
↳ replying to Lennie
But isn’t TCP 443 more secure?
EL
Eloisa 6 months ago
↳ replying to Lennie
Yeah, that sounds familiar!
KR
Kristeen 6 months ago
↳ replying to Lennie
I think TCP 443 is the right answer.
EU
Eun 11 months ago
↳ replying to Lennie
I remember TCP 80 being mentioned too.
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