It depends on a lot of factors. You gave us part of one, the server. It also depends on connectivity between the server and all the nodes, what combination of ICMP/WMI/SNMP you're using, how many resources there are to discover on each node, how many nodes actually exist in those ranges, etc.
I would start small with a Class C and see how it goes, just trial and error. It's likely going to take you a few weeks to finish. There's no reason you can't have overlapping discovery jobs, either. For example define a range that takes roughly 24 hours in your environment, and kick off one at the beginning of the day and one at the end of the day each day.
I have about 6 class B address to scan but I've split them all into /24. That way it's quick and easy to see where what is and what is available. I create a folder for each class B address and then when you click on it, it will open the 256 /24 subnets.
I then have a separate folder that just has each site listed and which ranges are there. This is the folder that always needs to be kept updated, whereas the /24 folders, just update themselves.
Things to bear in mind:
- Maximum run time of the discovery task is 10 hours
- The responsiveness of your network and parts of it are specific to you
- On average a class C discovery scan which is 50% populated will take around 10-15 minutes to complete
- Often when presented with this setup by customers i.e. several Class B networks often they have only a few hundred devices, so you can determine the true population of the networks to determine how you break up these scans
My advice - Break this up into smaller chunks and do so on two criteria; total number of addresses to scan keeping a single discovery job to no more than 5,000 and logical structure i.e. geographic or business unit
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Should it be timing out from a range of 5000 IPs? C class range x.x.9.0 thru x.x.30.255
I appreciate the input. Thanks