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Receive TCP RST packet from unreachable computer


Today I had a opportunity to work with wireshark.

I installed wireshark on my VMware and made some test on it.

And I found a interesting thing.

I sent the HTTP request to not exist computer and captured the all packet flow with wireshark.

The first packet was SYN packet.

And second one was re-transmission packet.(for system hadn't received any response from target computer).

But surprisingly, RST packet from the target computer reached.

I couldn't understand where this packet came from.

I tested for 2 target computers, and in both case, I had the RST packet.

So are there anyone answer about those suspicious RST packets?

Thanks for reading.


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asked 28 Jul '17, 00:48

Takuya%20Kimura's gravatar image

Takuya Kimura
accept rate: 0%

One Answer:


The most likely explanation is that a security device exists on the route towards the IP address of the non-existent computer, and that device forges the RST packet in the name of the nonexistent computer.

answered 28 Jul '17, 01:32

sindy's gravatar image

accept rate: 24%