Tuesday, October 1, 2019

How would you setup a semi-permanent packet capture for your WAN interface?

We have an application that requires a port-forward to function (according to the developers - it's niche software, so we don't have much room to argue). They won't disclose the IP addresses initiating a connection, so it's wide-open at this stage.

The router/firewall device is a Netgate appliance running pfSense 2.4.4. WAN circuit is 100 Mbps, although I would not expect to see much traffic, if any on the port-forwarded port?

What is the best way of setting up a long-term packet capture (filtering for the port-forwarded port), on the WAN interface?

The firewall appliance doesn't have a lot of storage (and it's a slow eMMC drive), so I assume I'd want to offload storage to another server on the network, right?

I assume I'd also want some kind of rotation going.

I've read there's tcpdump, dumpcap, wireshark etc.

What would people suggest here?

(Some people mention setting up a SPAN port - however, I assume that means I'd need another switch that sat in front of the WAN interface on the Netgate firewall, right?)



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