Thought I would share an experience with everyone...
All laptops on the network have the Cisco VPN client installed, as most take their laptops on the road or home when they leave at night.
One thing I've noticed when performing vulnerability assessments of the network with various tools, such as IS Scanner, STAT scanner, etc... is this:
If the client I am on has the VPN client installed and the machine I'm targeting has the VPN client installed, I cannot communicate to perform the scan.
ICMP traffic between the 2 devices will not work. This caused me quite a headache until I realized that the only common ground between all the clients I was trying to scan was the fact all were laptops.
All laptops also have personal firewalls for use when on the road. I thought this was the problem and removed the firewalls and still no success.
Finally I thought about the VPN client. So, on the source and the target device I stopped the "Cisco Systems, Inc. VPN Service" and VIOLA, I can scan all systems. Appears that if the source and target machines are running the service, they won’t communicate via ICMP.
