Scan Bandwidth (Discovery Scan)

The bandwidth level you select affects overall scan performance. The Medium bandwidth level is recommended as best practice in most cases.

High - Scan performance is optimized for high bandwidth usage resulting in the fastest possible scan time. As compared to the other levels, more netblocks are scanned in parallel, the netblocks contain fewer IPs so the processing is quicker, and the delay between groups of packets sent is shorter. While discovery scans run at the High bandwidth level may be faster to complete, they may overload firewalls and other networking devices.

Medium - Scan performance is optimized for medium bandwidth usage. Discovery scans at a Medium bandwidth level are well balanced between intensity and speed. This level is the recommended setting.

Low - Scan performance is optimized for low bandwidth network connections. As compared to the other levels, fewer netblocks are scanned in parallel, the netblocks contain more IPs, and the delay between groups of packets sent is longer. Discovery scans at a Low bandwidth level may take longer to complete.

Scan Bandwidth Settings

Each scan bandwidth level represents multiple settings. Compare the settings for each bandwidth level below.

Netblocks to Scan in Parallel

External Scanners - The maximum number of netblocks to scan at the same time per external scanner.

Netblock Size - The maximum number of IPs per netblock being scanned. The netblock specified for the domain is broken into smaller netblocks for processing. Each of these smaller netblocks equals a single scan process. This setting determines how many IPs will be included in each process. Show me an example

Example: Let's say you're performing a discovery scan on a Class B network (64000 IPs) using the Medium bandwidth level. For the Medium bandwidth level, the netblock size is set to 16384 IPs which means that the Class B range will be split into 4 netblocks. A separate scan process will handle each of these smaller netblocks, which completes faster than if you scanned all 64000 IPs in a single process.

Packet Delay

Each bandwidth level represents the delay between groups of packets sent to the netblocks being scanned. A short delay means that packets are sent more frequently, resulting in more bandwidth utilization and a shorter scanning time. A long delay means that packets are sent less frequently, resulting in less bandwidth utilization and a longer scanning time. The packet delay is set in seconds. Each bandwidth level has been assigned an appropriate delay time.

Setting	High	Medium	Low
Netblocks to Scan in Parallel: External Scanners	8	6	4
Netblocks to Scan in Parallel: Netblock Size	4096 IPs	16384 IPs	65536 IPs
Packet delay	Minimum	Minimum	Long