I have a need to setup accurate bandwidth monitoring temporarily to identify some issues with bandwidth consumption. To do this I understand I need to use netflow which is only available through a router. The problem is that I already have a firewall in place (a Juniper SSG). I have a Cisco PIX or ASA at my disposal but they too do not support netflow. My question is how can I setup a router to act transparently on the inside of my firewall to enable netflow and get accurate bandwidth statistics? It's nothing permanent. I just need to let it run for a week or so which is why I don't want to go through the hassle of getting a router with the firewall options, etc etc etc. I want to leave the current firewalls in place and drop in a router periodically to do some bandwidth testing then pull it out and drop it in another location at some other point. Kind of a mobile bandwidth monitoring idea.
Can anyone tell me how I can setup my Cisco 2600 to function transparently to achieve this goal? I don't want to setup a double NAT or change my firewall to run transparently and have the router do the NAT since that'll require too much work to simply drop it in, run bandwidth captures for a week, then pull it out.