Initial contact with devices is attempted using ICMP. Depending on your network, you can modify your scanning settings to expand or shorten delays between pings and the timeout.
- The number of pings should be set to 2 or higher, especially when scanning networks using Cisco routers. If the target IP address is not in the ARP cache of a Cisco router, the router discards the ICMP query (PING) while it requests the MAC address of the target IP. The first PING will never arrive at the subnet of the target IP address. In this situation, the Cisco router responds to the second PING.
- On slow connections, consider allowing more time between pings and expanding the timeout period.
- Click .
- Click the Preferences tab, and then specify the values in the Scanning grouping of the window.
- Click OK.