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Exam XK0-005 topic 1 question 26 discussion

Actual exam question from CompTIA's XK0-005

Question #: 26
Topic #: 1

A Linux administrator is troubleshooting SSH connection issues from one of the workstations.
When users attempt to log in from the workstation to a server with the IP address 104.21.75.76, they receive the following message:

The administrator reviews the information below:

Which of the following is causing the connectivity issue?

A. The workstation has the wrong IP settings.
B. The sshd service is disabled.
C. The server’s firewall is preventing connections from being made.
D. The server has an incorrect default gateway configuration.

Show Suggested Answer

Suggested Answer: C 🗳️

by TheRealManish at Oct. 23, 2022, 3:02 p.m.

Comments

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Nvoid

Highly Voted 2 years, 8 months ago

Selected Answer: C

It's a Firewall issue, i'm picking `C`. Please note, it's easy to misread the title of the outputs, read carefully -i made the same mistake from `TheRealManish` contribution also... it reads: Server Output#1 Server Output#2 Server Output#3 Server Output#4 *NOT* Server #1 Output Server #2 Output Server #3 Output Server #4 Output Cheers!

upvoted 7 times

TheRealManish

2 years, 8 months ago

OMG thanks so much! i totally missed the wording!! i was like why the F is it telling us all of these other outputs!

upvoted 2 times

TheRealManish

2 years, 8 months ago

Thanks again, but im reading thru this and the firewall rejection is to reject with ICMP.. but instead it is rejecting with TCP reset. It seems like C is also wrong, but its way closer than all of the rest.

upvoted 2 times

Nvoid

2 years, 8 months ago

TCP/IP defines the kernel will send an ICMP message back with an "Port unreachable" message for UDP services, and TCP RST messages for TCP - REF: https://unix.stackexchange.com/questions/261360/icmp-port-unreachable-error-even-if-port-is-open So from what i can tell, TCP response from the server should be sending a RST not a ICMP "Port unreachable" message, thats for udp!

upvoted 1 times

Nvoid

2 years, 8 months ago

Glad we're working together, i figured you would have taken your test already and passed.

upvoted 1 times

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Aj26a

Most Recent 1 year, 2 months ago

Selected Answer: C

From the provided outputs and error message, the connectivity issue seems to be caused by the server's firewall configuration. Specifically, Server Output 1 shows that the firewall on the server is configured to reject SSH connections (port 22) from several IP addresses, including 5.189.153.89, which matches the IP address of the workstation.

upvoted 3 times

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BryanSME

1 year, 8 months ago

This statement on Server output 2: "Active: active (running) since" means that even tho the service did not load at startup, it has been manually started, manually starting `sshd`: ❯ sudo systemctl start sshd ❯ sudo systemctl status sshd ● sshd.service - OpenSSH Daemon Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor preset: disabled) Active: active (running) since Tue 2020-07-14 11:13:08 -03; 2s ago From https://bbs.archlinux.org/viewtopic.php?id=257365 That leaves the firewall issue as correct.

upvoted 1 times

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Cieliog

1 year, 10 months ago

Selected Answer: B

Comptia is famous for these gotcha questions. C is probably correct, but B is probably the Comptia answer.

upvoted 2 times

clair12

10 months ago

might not be B actually, sshd seems to have been running for the past two weeks

upvoted 1 times

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mrtwister76

2 years, 2 months ago

Firewall issue

upvoted 1 times

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Rob74613

2 years, 3 months ago

Selected Answer: C

As the question states the user tried to ssh from ONE of the workstations, and one of the workstations (Workstation 1) has an IP that is being rejected in the firewall with port 22 (aka ssh)

upvoted 1 times

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ominousred

2 years, 4 months ago

I selected "B" because if you take any service and DISABLE it, it will not work. In this case, ssh is disabled.

upvoted 1 times

CodeMaestro

2 years, 2 months ago

Yes the ssh service is disabled but as you can see it has been running, what that means is that the service does not start up automatically but needs the administrator to actively start it up, but the firewall drops the packets from port 22 and thus it is a firewall issue.

upvoted 2 times

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linux_admin

2 years, 5 months ago

Selected Answer: C

The server’s firewall is preventing connections from being made.

upvoted 1 times

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bjornborg

2 years, 9 months ago

Selected Answer: C

Server output 2 -> sshd "active (running)", so answer not B :-( Server output 1 -> port 22 being blocked from all sources ... firewall issue Everything else looks fine

upvoted 3 times

TheRealManish

2 years, 8 months ago

MODS, I think i might have hit the flag button by accident, please disregard . the output says we are connecting to the server ending in .76. Thats server 3. so we ignore all of the output for server 1,2,4. All we know about 3 is that it has an IP address. If a service is not running on a machine, it will send a connection refusal..

upvoted 1 times

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TheRealManish

2 years, 9 months ago

It seems like B to me.. as Server 3 seems to set the correct IP. receiving a reset packet back indicates a service is not running.

upvoted 1 times

Veteran903

2 years, 8 months ago

server output is telling you ssh is active and running, also, as you can see the firewall is rejecting all connections so this is clearly a firewall issue, definitely C

upvoted 1 times

TheRealManish

2 years, 8 months ago

are you sure? it says we are connectiong to host 104.21.75.76. thats server 3. therefor the ONLY output we should concern ourselves with is the output from server 3. the server 3 output is super vague. no talk about firewall or ssh port. i wish we had a way to get together and review this stuff :)

upvoted 1 times

TheRealManish

2 years, 8 months ago

disregard my comment here, apparently, I can't read lol.

upvoted 1 times

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