How many probes you need

Summary

How many Scout probes you need depends on how your network is split. The rule is simple: one probe per segment, meaning one per VLAN or subnet. This lesson explains why, what happens to a network that has no probe of its own, and how to do the count before you start.

Chapters

Key points

• One probe per segment. Every VLAN or subnet you want to analyse in depth needs a probe installed on a machine in that segment.
• The reason is ARP. To find devices, the probe also uses ARP: it asks every address who is there, and the devices answer. ARP only works inside a single segment and does not cross routers. A probe in the office network does not see the production devices in the same detail when a router separates the two networks.
• Networks behind a router. If a network can only be reached through routing, the probe scans it in a reduced mode: no MAC addresses and fewer ports checked. RECON flags this and recommends using a probe that sits on that network.
• Unreachable does not mean empty. A network the probe cannot reach is not shown as empty: RECON marks it Unreachable. You know straight away that a probe is missing there, not that the network is safe. If the network was really scanned and no device answered, you see No live hosts instead.
• Other coverage states. When coverage is incomplete, RECON uses explicit states such as Coverage not established, Throttled, Blocked or Partial. In all of these cases a low device count is not a reliable result.
• How to count them. Start from the list of networks: five networks need five machines, one per network, each with its own probe. Three branch offices with two VLANs each make six probes.
• Ask your network team for the list. Your network team has the exact list of VLANs and subnets: get it before you start.
• Several probes together. When you have more than one probe, you can group them in RECON with Add probe group and analyse them in a single scan.

Transcript

The full transcript (in Italian) is in the Transcript tab of the player.

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