No inbound packets observed

[Farzana]

Hello,

Trying to troubleshoot an issue of aged-out traffic flow. It was SSH traffic originated from customer's LAN and destined to Internet address. Packet capture was configured on the firewall for troubleshooting but only outbound (but no inbound) packets were observed inside the PCAP files. Tried via WebGUI and CLI.

Could it be that the incoming packets were dropped before the capture process, or packets never reached the firewall?
How to confirm?

Thanks in Advance.

[bmorris1]

Hi Farzana,

You can check the 'pre-parse' option to check for packets before they hit the recieve stage of the firewall, this is usually layer 2 packets that do not traverse the firewall so have no need to go to the recieve stage. Other than that it looks like you have answered your own question, no packets being recieved by the firewall.

hope this helps,

Ben

[reaper · Accepted solution]

don't do the pre-parse without checking the dataplane 'load' beforehand, this option will bypass any filter definition you have set

if there's a lot of traffic, everything will be captured and your capture will become unuseable

did you follow the instructions in the guide: Getting Started: Packet Capture

I usually add a set of filters for the reverse flow, just in case the returning packets get dropped for some reason (the filter/capture is session aware, but if for example the returning packets got malformed or the sequence number is somehow altered, the packets may get discarded)

so i'd go, for example

filter1 src 10.0.0.1 dst 4.2.2.2

filter2 src 4.2.2.2 dst <NAT ipaddress> 198.51.100.1

is the session also indicating 0 packets received (show session id <#>)?