Switch discovery

Optional discovery finds switches with TCP connection checks, ping, the ARP cache, SNMP identity and LLDP/CDP neighbours. Ranges are limited to /22.

What discovery sends

Discovery uses the checks below. The ARP cache read sends no network traffic. Gateway probes target gateway addresses. Discovery does not use nmap.

Which ranges it scans

When you start a scan, you can name one subnet of /22 or smaller. If you name none, the scan covers the /24 segment of the appliance.

Discovery builds its segment list from these sources:

• segments of known devices and registered switches;
• segments found by gateway probes;
• management addresses from LLDP and CDP neighbour data;
• the segments of the appliance itself.

The LLDP and CDP crawl

The crawl starts from a switch that you name and follows its LLDP and CDP neighbour tables.

• It goes only to the management addresses that the neighbour tables name. It does not sweep a range.
• By default, the crawl follows up to 3 neighbour hops and stops at 128 network devices.
• The crawl keeps a link only when each device lists the other device as a neighbour.
• The crawl lists candidate switches next to switches already added as sources.

Run a scan

Any signed-in user with read access can start a scan. The appliance records each scan in the audit log. See Audit log and the auditor evidence pack.

1. Open a switch page.
2. Below the faceplate, select Scan for switches.
3. Enter the subnet to scan, or a seed switch for the LLDP and CDP crawl.
4. Start the scan.
5. Wait for the list of candidate switches. Each candidate shows its identity and whether it answers.
6. Before you add a candidate, review it.

If Scan for switches is not shown, your installation hides the setup actions on switch pages. Ask an administrator to run the scan.

From candidate to read-only source

A person with the role to manage sources tests credentials and adds a found switch as a read-only source.

1. Select a candidate switch.
2. Enter the read-only credentials for the switch.
3. Test the credentials.
4. If the test passes, add the switch as a read-only source.
5. Open Connectors.
6. Check the new source.

After you add it, Devexana reads the switch on its schedule. See Switches over SSH and SNMP. Its neighbour data then appears on the network views. See Network views: campus map and switch faceplate.

Limits