Foglight Experience Monitor 5.8.1

Automatically discovering subnets

The auto-discovery process examines monitored network traffic and constructs possible subnets that may be in use on your network. It is not possible for the appliance to determine the exact subnets that are in use because that information is not available in the traffic. Instead, the appliance uses the client IP addresses extracted from the IP headers in the traffic or from the x-forwarded-for HTTP header tag, and constructs a class C subnet that might be in use on your network. You may need to edit the mask portion of the subnet to match your actual subnets. The page updates every few seconds expanding the list of subnets as they are discovered.

On the Subnets page, click Auto-Discover Subnets link if you would like the appliance to suggest possible subnets that you want to configure.

Click Stop at any time to stop the auto-discover process and use the subnet list that has been compiled up to that point. All subnets that have been detected are listed (see the following illustration).

The following information displays in the returned list of Subnets.

Table 13. Information displayed for subnets
Data	Definition
Subnets	Displays the subnet number.
Client Packets	The number of client packets being transmitted from clients to the server. NOTE: If the packet count is zero and the Server Packet value is greater than zero the network tap is not configured correctly.
Server Packets	The number of packets being transmitted from the server to clients. NOTE: If the packet count is zero and the Client Packet value is greater than zero the network tap is not configured correctly.
New TCP Connections	The number of TCP connections that have been observed on the server. NOTE: If the number of connections equals zero or the number is small in relation to the number of active connections, the load balancer is maintaining a limited number of TCP connections to the web server and using the proxy server to send all requests over the TCP connections.
Active TCP Connections	The number of active TCP connections discovered in the traffic for the subnet.

Select the check boxes for the subnets that you want the appliance to monitor.

Click Add.

You are returned to the main Subnets page, and all newly added subnets are now listed.

Checking for overlapping subnets

Subnet definitions may be defined so that they overlap, meaning that a particular IP address will match more than one subnet definition. Trying to assess which subnets definitions are overlapping can be a difficult task to accomplish. Using the subnet mask, the system can determine whether subnet definitions are including the same IP address.

Clicking Overlap Check at the bottom of the Subnet page launches the Subnet > Overlap Check page, which lists pairs of subnets and their subnet masks. Using the subnet mask, you can identify which part of the IP address is shared by each of the subnets.

For example, in the following screen shot, AV Training shares the same IP prefix as Aliso Viejo.

Figure 51. Subnets: Overlap Check page