I have several tabs open to several switches and routers in the WebUI. I'm using the troubleshooting tab to create a few PCAP files. The issue occurs in both chrome or firefox, so I dont think it's a browser issues specifically, but some of the time I'm unable to "export to desktop".
The packet capture feature (EPC) in the web interface is very intuitive and easy to use. It's simply using the monitor capture commands but using it in the web ui allows you to download using HTTPS and in this environment that is the only option available, so it's invaluable.
When it works you click the Export button and a window pops up allowing you to choose several options, default being "my desktop" which just allows you to download it directly to your PC. When it doesn't work and you select "my desktop" the browser errors out stating it can't find the selected file. However you can immediately select export once again and select flash: and it will create the pcap as bootflash:WebUITmp.pcap which you can then browse to in file manager and download it that way (which i found in another thread here) however it's a multi step process that's for some reason unnecessary at times.
The one thing is if *it is* a browser problem, which again, multiple tabs open and on some they download fine and others I get this problem, developer tools is disabled by security so I don't have that luxury...
