How to find network problems?

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alex_ak12020-02-05 07:53:10

Computer networks

alex_ak1, 2020-02-05 07:53:10

Hello.
I mirrored the port on the smart switch and looked at the number of retransmits using wireshark. Now about 4% of packets are stable - retransmits. Is this normal or already bad?
And immediately the question is - how to find the culprit? Will be connected so on ports that there were minimum sizes of segments and to look who is guilty?

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3 answer(s)

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DDwrt100, 2020-02-05
@DDwrt100

Well, you have the culprits, the dump should contain ip addresses. First of all, look at the load on the host ports, whether there are resets, the buffers on the adapters are not overflowing. And of course, check for losses.
It is also worth considering that in a normally working network, retransmits may be due to the peculiarities of the TCP protocol, and to some extent this is a normal phenomenon.

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Wexter, 2020-02-05
@Wexter

4% of packages - retransmits

retransmits appear at losses. Losses occur either due to problems with the port / cable / software, or due to port overload. If the port is not overloaded anywhere at the same time - look at some hosts for retransmits or different ones, from there and dig in the direction of finding the cause. It is possible that just some software is a little inadequately working.