I want to double check, if the following scenario with NAT on both sides is supported. Topology:
SJ-Win-Probe1 10.10.20.20 --- Cisco Router with Public IP 63.x.y.z ----- public internet ------- AWS IGW Public IP 3.a.b.c --- Win-Probe2 10.53.1.20
Cisco Router is doing static NAT, mapping all ports 1:1 between 10.10.20.20 and 63.x.y.z. Both remote probes are registered successfully, ping, health, windows-related sensors are working fine.
QoS (Quality of Service) One Way works also good. The problem is with round trip test, which we need for MOS score - it is failing. Round trip sensor is defined with PRTG probe AWS using public IP 3.a.b.c
Sensor is failing with the following message:
"This sensor has not received any data since startup. There seems to be a problem with the UDP port of the Qos Sensor (Port 50000 already in use?)."
Did wireshark traces on both sides. SJ-Win-Probe1 sends packets out, wireshark traces on AWS shows packets arriving on UDP 50000 port with source of Cisco Router 63.x.y.z and destination 10.53.1.20. The AWS-Win-Probe2 does NOT sends ANY packets back.
Potential reason: AWS-Win-Probe2 has the public IP 3.a.b.c (elastic IP from AWS assigned to the Ethernet interface), but the AWS-Win-Probe2 has private IP 10.53.1.20 configured on the NIC. This is the normal configuration on AWS - the IGW is connected to this VPC and they do 1:1 NAT between public 3.a.b.c. and private 10.53.1.20.
- is the round trip test supported in such topology?
- why the Endpoint2 does not reply back to the Endpoint1?
- can we have a quick meeting in order to troubleshoot it? I am based in San Jose, we have 9 hours time shift to Germany, wir koennen auch Deutsch reden. :-)