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Exam AWS Certified Solutions Architect - Associate SAA-C03 topic 1 question 218 discussion

A company has a web server running on an Amazon EC2 instance in a public subnet with an Elastic IP address. The default security group is assigned to the EC2 instance. The default network ACL has been modified to block all traffic. A solutions architect needs to make the web server accessible from everywhere on port 443.

Which combination of steps will accomplish this task? (Choose two.)

  • A. Create a security group with a rule to allow TCP port 443 from source 0.0.0.0/0.
  • B. Create a security group with a rule to allow TCP port 443 to destination 0.0.0.0/0.
  • C. Update the network ACL to allow TCP port 443 from source 0.0.0.0/0.
  • D. Update the network ACL to allow inbound/outbound TCP port 443 from source 0.0.0.0/0 and to destination 0.0.0.0/0.
  • E. Update the network ACL to allow inbound TCP port 443 from source 0.0.0.0/0 and outbound TCP port 32768-65535 to destination 0.0.0.0/0.
Show Suggested Answer Hide Answer
Suggested Answer: AE 🗳️

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Chosen Answer:
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Parsons
Highly Voted 1 year, 5 months ago
Selected Answer: AE
A, E is perfect the combination. To be more precise, We should add outbound with "outbound TCP port 32768-65535 to destination 0.0.0.0/0." as an ephemeral port due to the stateless of NACL.
upvoted 16 times
oguzbeliren
11 months, 1 week ago
What is the main reason that you are using the TCP port 32768-65535> In the question, it doesn't ask you any requirement about it.
upvoted 4 times
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MohammadTofic8787
9 months, 3 weeks ago
i Think AD because acl is stateless we must open the port outbound and inbound , in option c we only open 443 on inbound
upvoted 2 times
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MohammadTofic8787
9 months, 3 weeks ago
i Think AD because acl is stateless we must open the port outbound and inbound , in option E we only open 443 on inbound
upvoted 3 times
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pentium75
Highly Voted 6 months, 1 week ago
Selected Answer: E
For me it's grammatically unclear whether "port 443" and "port 32768-65535" in answers D and E are referring to the source or destination ports of the outbound traffic. If source ports then it would be D. If destination ports (which seems more likely) then it's E. "On Windows, the ephemeral port range is usually from 49152 to 65535. On Linux, it is often from 32768 to 61000." Thus 32768-65535 would cover both Windows and Linux.
upvoted 10 times
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lofzee
Most Recent 1 month, 1 week ago
Selected Answer: AE
Security group only needs inbound rules. ACL needs inbound and outbound.. Outbound traffic is going to be dynamic ports. Answer is A and E
upvoted 2 times
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sidharthwader
4 months ago
AE Security group is a stateful resource and can understand to allow traffic from source 0.0.0.0/0 with port 443 but ACL is stateless so traffic that is allowed inside the network we must configure the same to go outside the network as well.
upvoted 1 times
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awsgeek75
6 months ago
Selected Answer: AE
https://docs.aws.amazon.com/vpc/latest/userguide/vpc-network-acls.html#nacl-basics "NACLs are stateless, which means that information about previously sent or received traffic is not saved. If, for example, you create a NACL rule to allow specific inbound traffic to a subnet, responses to that traffic are not automatically allowed. This is in contrast to how security groups work. Security groups are stateful, which means that information about previously sent or received traffic is saved. If, for example, a security group allows inbound traffic to an EC2 instance, responses are automatically allowed regardless of outbound security group rules." A fulfils the security group requirement E is the only option that explicitly covers outbound traffic and ports. D covers outbound destination but given that all traffic is blocked (as per the question) this won't work
upvoted 3 times
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[Removed]
7 months, 2 weeks ago
Selected Answer: AC
For typical web server scenarios, such as serving content over HTTPS (port 443), you generally do not need to explicitly open outbound ports in the network ACL (NACL) for the return traffic.
upvoted 1 times
pentium75
6 months, 1 week ago
But NACLs are stateless."The default network ACL has been modified to block all traffic"; if you don't allow any outbound traffic then the web server won't be able to reply to clients.
upvoted 2 times
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TariqKipkemei
9 months, 2 weeks ago
Selected Answer: AE
ACL is stateless. you have to define both inbound and outbound rules.
upvoted 2 times
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MohammadTofic8787
9 months, 3 weeks ago
i Think AD because acl is stateless we must open the port outbound and inbound , in option c we only open 443 on inbound
upvoted 2 times
MohammadTofic8787
9 months, 3 weeks ago
i Think AD because acl is stateless we must open the port outbound and inbound , in option D we only open 443 on inbound
upvoted 1 times
MohammadTofic8787
9 months, 3 weeks ago
please admin delete this , sorry
upvoted 1 times
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MohammadTofic8787
9 months, 3 weeks ago
please admin delete this , sorry
upvoted 1 times
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Guru4Cloud
9 months, 4 weeks ago
Selected Answer: AE
A, E is perfect the combination. To be more precise, We should add outbound with "outbound TCP port 32768-65535 to destination 0.0.0.0/0." as an ephemeral port due to the stateless of NACL.
upvoted 3 times
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beginnercloud
10 months, 1 week ago
Selected Answer: AE
AE is the best answer here, but in reality, E is not good enough. Here, it says that the client chooses the ephemeral port, and it can start from 1024. Only Linux clients have the range starting at 32768 https://docs.aws.amazon.com/vpc/latest/userguide/vpc-network-acls.html#nacl-ephemeral-ports Unless the destination advertises the ephemeral ports, which I don't think is the case
upvoted 1 times
pentium75
6 months, 1 week ago
"On Windows, the ephemeral port range is usually from 49152 to 65535. On Linux, it is often from 32768 to 61000." Combined: 32768 - 65535 ...
upvoted 2 times
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Thornessen
11 months, 2 weeks ago
Selected Answer: AE
AE is the best answer here, but in reality, E is not good enough. Here, it says that the client chooses the ephemeral port, and it can start from 1024. Only Linux clients have the range starting at 32768 https://docs.aws.amazon.com/vpc/latest/userguide/vpc-network-acls.html#nacl-ephemeral-ports Unless the destination advertises the ephemeral ports, which I don't think is the case
upvoted 2 times
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Abrar2022
1 year, 1 month ago
32768-65535 ports Allows outbound IPv4 responses to clients on the internet (for example, serving webpages to people visiting the web servers in the subnet).
upvoted 1 times
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WherecanIstart
1 year, 3 months ago
Selected Answer: AE
NACL blocks outgoing traffic since it is infact stateless..Option E allows outbound traffic from ephemeral ports going outside of the VPC back to the web.
upvoted 2 times
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Brak
1 year, 4 months ago
It can't be C, since the current NACL blocks all traffic, including outbound. Need to allow outbound traffic through the NACL. But E is a bad answer, since ephemeral ports start at 1024, not 32768.
upvoted 2 times
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neosis91
1 year, 4 months ago
Selected Answer: AC
A and C not E Option E states to allow incoming TCP ports on 443 and outgoing on 32768-65535 to all IP addresses (0.0.0.0/0). This option only allows outgoing ports and does not guarantee that incoming connections on 443 will be allowed. It does not meet the requirement of making the web server accessible on port 443 from anywhere. Therefore, option C which states to allow incoming TCP ports on 443 from all IP addresses is the best answer to meet the requirements.
upvoted 5 times
Deepak_k
1 year, 4 months ago
Answer : AE - Incoming traffic on port 443 but sever can use any port to reply back.
upvoted 2 times
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JoeGuan
10 months, 2 weeks ago
It seems there are lots of questions that ask for minimum requirements, and often times adding 'things' to the solution are not correct. I am not sure about this question and I would pick C. E adds ambiguity. What if you only needed to open ports for Lambda? That would be a different set of ports. I think E adds some assumptions into the question. I think opening some ports for some assumptions and keeping ports closed for other assumptions is not correct. The best assumption is to assume they are asking how to open ports for 443
upvoted 1 times
slackbot
10 months, 2 weeks ago
E still guarantees something will work. C definitely means - nothing will work, because you are not allowing egress traffic at all
upvoted 2 times
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slackbot
10 months, 2 weeks ago
seems like either you did not read what you wrote "Option E states to allow incoming TCP ports on 443 and outgoing on 32768-65535 to all IP addresses (0.0.0.0/0)." (because first part of the sentence allows incoming 443) or you do not understand how ACLs work - they are STATELESS, which means, you need to allow both IN and OUT, not just IN like SGs which are stateful. if they were the same - what would be the purpose of the ACLs?
upvoted 1 times
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Aninina
1 year, 5 months ago
Selected Answer: AE
AE correct
upvoted 3 times
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techhb
1 year, 5 months ago
Selected Answer: AE
A & E , E as NACL is stateless.
upvoted 2 times
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Community vote distribution
A (35%)
C (25%)
B (20%)
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