Nagios Support Forum

hello all,
Is it possible to run a scan across multiple subnets with /16 subnet mask? In theory it would scan 65536 IP addresses.
Any ideas how long this scan would take to complete and if the accuracy of the results would be affected by the large number.

Also, I have run a scan across a subnet and some servers have been found and some not (that I know exist on that subnet).
Would it be that certain ports need to be opened up perhaps?

You should be able to run a scan on that but I'm sure it would take a long time (this varies a lot based on how many active devices you have so it's not something I can estimate).

If your systems (or firewalls/security devices in the path) are blocking pings/icmp I could see them not being listed in there.

The scan really just looks at the 1000 most common ports but it uses a ping sweep to find the hosts to scan.