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fluzocapacitor's avatar
fluzocapacitor
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Jun 10, 2024

Issue with Capturing SYN-ACK Packets on F5 BigIP Virtual Server

Hello everyone, I have a virtual server set up on an F5 BigIP. I captured traffic on a client (IP: 10.16.x.x) of the balanced service and on the virtual server itself (IP: 10.16.y.y). On the client ...
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wendelyes's avatar
wendelyes
Icon for Altostratus rankAltostratus
Jun 11, 2024

Hello,

 

The traffic in the packet captures could be hidden if it is offloaded. This use to happen in fastL4 virtual servers and you can disable it by changing to Standard modifying the fasL4 profile.

Anyway, in this case I would bet that the SYN-ACK is goign through other device and the F5 is not seeing it. The F5 is forwarding the SYN packet and blocking the other traffic coming from the client because the session is not established yet. The reset you have at the end is created by the f5 because the session could not be established.

I think the best way to know where this SYN-ACK is going through is to capture the traffic in the client and check the source mac. This way you can probably check who is sending it.

 

Regards