See page 20 of the NPM Admin Guide here
Enabling Secure Channels with SSL
Orion NPM supports the use of Secure Sockets Layer certificates to enable secure communications with the Orion Web Console. The following procedure enables SSL connections to the Orion Web Console.
Secure SSL communications are conducted over port 443.
The following procedure does not detail the process of either obtaining a required certificate or generating a certificate signing request for a third-party certificate authority. It is assumed that the required SSL certificate has already been installed on your Orion NPM server. For more information about acquiring and installing a required server certificate for SSL communications, see http://support.microsoft.com/kb/298805, from which the following procedure was adapted.
To enforce SSL connections to the Orion Web Console:
1. Log on as an administrator to your Orion NPM server.
2. Click Start > Control Panel > Administrative Tools > Computer Management.
3. Expand Services and Applications > Internet Information Services (IIS) Manager > Web Sites.
4. Click SolarWinds NetPerfMon.
5. Click Action > Properties.
6. Click the Web Site tab.
7. Confirm that SSL port is set to 443.
8. Click Apply.
9. Click Advanced.
10. If the Multiple SSL identities for this Web site field does not list the IP address for the Orion Web Console with SSL port 443, complete the following steps.
a. Click Add, and then select the IP address of the Orion Web Console.
Note: As it was set initially in the Configuration Wizard, this option is usually set to (All Unassigned). If the IP address of the Orion Web Console was not initially set to (All Unassigned), select the actual, configured IP address of the Orion Web Console.
b. Type 443 as the TCP port, and then click OK.
11. Click the Directory Security tab.
Installing SolarWinds Orion Network Performance Monitor 21
12. Click Edit in the Secure communications section.
13. Check Require secure channel (SSL).
14. Select Accept client certificates in the Client certificates area.
15. Click OK on the Secure Communications window.
16. Click Apply, and then click OK to exit.