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How do I reuse or restrict burp's source ports

keith | Last updated: Jul 16, 2017 06:06PM UTC

I'am using intruder configured with 50 threads. It seems that on each request burp uses new source port. The gateway router NATs every request on a separate port. Each 16300 requests intruders requests are dropped for couple of minutes. It seems that the router doesn't provide new ports. During the drops the router probably waits to timeout all the allocated ports which have been used only once. Afterwards it can allocate the ports once again and the intruder continues his requests for another set of 16300. Anyone has an idea how to make intruder's threads to reuse ports or set a specific range which ports to use as source ports?

PortSwigger Agent | Last updated: Jul 17, 2017 07:09AM UTC

Hi Keith, Thanks for your inquiry. I'm afraid Burp doesn't have the ability to control source port allocation. It sounds like your NAT router is maintaining the connection state after the TCP connection has terminated, and timing out after a couple of minutes. We've found that some NAT gateways have issues like this that make them unsuitable for heavy duty scanning. We recommend you use a different router, as many routers do handle this correctly, and here we frequently run large scans through our NAT gateway, without issues. Please let us know if you need any further assistance.

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