Network Management

NetPath last hop shows high latency

The NetPath last hop shows high latency when dealing with ASA. Network Performance Monitor(NPM) version 2020.2.1

First published date

10/25/2018 8:27 PM

Last published date

10/25/2018 8:27 PM

Overview

The NetPath last hop shows high latency when dealing with ASA.

Product section

Network Performance Monitor

Cause

NetPath standard probing sends multiple rounds of SYN packets to the endpoint. The endpoint responds to each SYN with SYN-ACK. Typically, OS on NetPath probe catches SYN-ACK and responds with RESET packet which clears the half-open connection in ASA. So the ASA treats the next SYN for a new half-open connection. 

 

In some rare cases, OS doesn't send RESET. ASA would catch an extra SYN for the existing half-open connection and may consider an anomaly. The SendResetPerRoundStandard flag basically forces NetPath probe to send the RESET packet by itself so it clears out the half-open connection in ASA.

Resolution

  1. Go to C:\ProgramData\Solarwinds\Orion\NetPath\NetPathAgent.cfg on the SolarWinds server.
  2. Set the SendResetPerRoundStandard value to True.
  3. Restart all services.