Menu
I am sending UDP packets from one PC to another. I am watching the the whole activity using Wire Shark. I notice that for some time there is smooth transmission of packets from one system to the other. Then suddenly ICMP packets with error 'port unreachable' starts to appear. Then they disappear for some time and there is again smooth transmission of UDP packets. Then these ICMP packets again appear with the same 'port unreachable' error. Then these ICMP packets disappear again and so on. And this continues in a periodic manner.
Can anybody shed some light that what could be the reason for it.
691
About ICMP destination unreachable messages A device sends ICMP destination unreachable messages by following these rules: The device sends the source an ICMP network unreachable message when the following conditions are met: The packet does not match any route. No default route exists in the routing table.
The ICMP Port Unreachable message originates from a host, not a router. The indicated port process was either not running or was swapped out. SNMP (Port 161) is a common port to be missing.
ICMP has no concept of ports, as TCP and UDP do, but instead uses types and codes. Commonly used ICMP types are echo request and echo reply (used for ping) and time to live exceeded in transit (used for traceroute).
User receives a Destination host unreachable message on sending a ping request. This issue typically indicates that the host is down or otherwise not returning ICMP echo requests. It is also possible that an intermediate network hop is dropping the packets.
One odd error that might be associated with a Port Unreachable message is seen when an otherwise normally operating conversation is interrupted by a Port Unreachable message. When you inspect the conversation you observe that the unreachable port was working without a problem. Frames were going to and from the port number when, suddenly - Port Unreachable. 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
151
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
