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+15 votes

These are the six choices. Choose all correct answers

a. Echo Reply
b. Destination Network Unreachable
c. Destination Port Unreachable
d. Destination Host Unreachable
e. Echo Request
f. TTL expired

This is actually a question from the Stanford course video 2-3.

asked in CSC335_Spring2019 by (3.1k points)
edited by

1 Answer

+9 votes

b. Destination Network Unreachable
d. Destination Host Unreachable
f. TTL expired

I wonder why it's not the case for Destination Port Unreachable though?

answered by (3.1k points)
edited by
+6

It is no? since you did specify Destination Host Unreachable in your answer.

+6

Edited! I actually meant Destination Port Unreachable, tks for pointing that out

+5

Perhaps because we don't find out that the port is unreachable until it gets to the target host computer, so it would be the target host that responds with that ICMP packet, and not the router? (although I'm not sure that many hosts would be polite enough to send a response packet...?)

+4

So would it mean that the Destination Port Unreachable ICMP messages never get sent at all?

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