CLEAR-Flow is a broad framework for implementing security, monitoring, and anomaly detection in ExtremeXOS software. Instead of simply looking at the source and destination of traffic, CLEAR-Flow allows you to specify certain types of traffic that require more attention. After certain criteria for this traffic are met, the switch can either take an immediate, predetermined action, or send a copy of the traffic off-switch for analysis.
CLEAR-Flow is an extension to Access Control Lists (ACLs). You create ACL policy rules to count packets of interest. CLEAR-Flow rules are added to the policy to monitor these ACL counter statistics. The CLEAR-Flow agent monitors the counters for the situations of interest to you and your network. You can monitor the cumulative value of a counter, the change to a counter over a sampling interval, the ratio of two counters, or even the ratio of the changes of two counters over an interval. For example, you can monitor the ratio between TCP SYN and TCP packets. An abnormally large ratio may indicate a SYN attack.
The counters used in CLEAR-Flow are either defined by you in an ACL entry, or can be a predefined counter. See Predefined CLEAR-Flow Counters for a list and description of these counters.
If the rule conditions are met, the CLEAR-Flow actions configured in the rule are executed. The switch can respond by modifying an ACL that will block, prioritize, or mirror the traffic, executing a set of CLI commands, or sending a report using a SNMP trap or EMS log message.
Note
CLEAR-Flow is available on platforms with an Edge (or higher) or Base (or higher) license. For more license information, see the ExtremeXOS v33.1.1 Licensing Guide document.CLEAR-Flow is supported only on ingress. Any limitations on a given platform for a regular ACL also hold true for CLEAR-Flow.