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Unreachable TCP ports notably respond with TCP RST rather than a Destination Unreachable type 3 as might be expected. So indeed, your UDP scanning to port 80/UDP simply receives an ICMP unreachable message back because there is not a service listening to that combination or protocol/port.
28 sie 2009 · Folks, from a Windows PC I can do "telnet IP 80" in order to test TCP port status on target host. Any similar command in IOS?
8 lip 2013 · This is indicative of an overload condition or process priority configuration problem in the reporting host. The process in question was swapped out of memory and was not able to swap back in quickly enough to avoid the unreachable indication. Source: https://www.savvius.com/resources/compendium/tcp_ip/unreachable#port_unreachable
Nothing is listening on the IP:Port you are trying to connect to. The port is blocked by a firewall. No process is listening. This is by far the most common reason for the message. First ensure that you are trying to connect to the correct system.
6 sie 2020 · Correct, it seems like the tunnel port is unreachable, but the HTTPS port is reachable just fine. Normally 5090 would be your tunnel port (by default unless you changed it during setup). You will have to ensure that it is reachable from the outside (the wider internet).
11 paź 2019 · The ICMP Destination Port Unreachable prevents the majority of this data from ever being sent. It doesn't need to be processed/sent by C, it doesn't need to transit the network(s) between C and S, and it doesn't need to be received and processed in any form by S.
17 kwi 2021 · The message is from the destination host saying that the original datagram is unable to reach the port on the destination host. The IP packet made it to the IP process in the network stack of the destination host, but the transport protocol rejected the transport datagram, sending back the ICMP error message..
