Active-Measurement Group Configuration

You need to enable EFC collection within each active measurement group where you want endpoints to be used as probe targets, with the efc enable command.

Use the efc filter command one or more times to identify the access lists you want to use for the active measurement group.

You can also define which addresses from within the flow you want to be used as target addresses, with one or more of the following commands:

• efc bytes minimum--specifies a minimum amount of traffic volume a prefix must have
• efc bytes top--lets you pick prefixes by volume of traffic
• efc last-update-within--specifies a time interval within which a prefix must have been updated
• efc exclude-prefix--excludes a specific prefix by address
• efc source--selects either Netflow or SPAN data

The access list used here, filter_traffic, was defined in the previous example.

When you enter the active-measurement group command for an existing group, subsequently entered commands will be added to the existing group configuration block:

Avaya_ANS(config)# module engine
 
Avaya_ANS(config-engine)# active-measurement group efc_targets
 
Avaya_ANS(config-engine-active)# efc enable
 
Avaya_ANS(config-engine-active)# efc filter filter_traffic
 
Avaya_ANS(config-engine-active)# efc source netflow 192.168.1.16
 
Avaya_ANS(config-engine-active)# efc bytes top 3
 
Avaya_ANS(config-engine-active)# end
 

The efc enable command in the example enables EFC in the active-measurement group efc_targets, which should already have been configured as described in Chapter 5: Configuring Agent-Based Measurement.

The efc filter command means the data stream from which the active-measurement group will obtain its target endpoints will be filtered by the access-list filter_traffic, defined in the previous example.

The efc source command limits EFC targets for this active-measurement group to endpoints gathered from the Netflow stream originating on the router interface 192.168.1.16.

The efc bytes top command means that from that stream, only the three most heavily trafficked prefixes will be probed.

CNA also has the ability to define membership in efc-defined active-measurement groups based on BGP source-as. (This function requires that EFC is configured with the NetFlow option; no BGP source-as information is available to the EFC module via the SPAN/Monitor function.)

There are two steps to configure this option:

1. Define an ip as-path access-list

ip as-path access-list 101 permit 45000

2. Include that as-path access list in an efc filter within an active-measurement group.

active-measurement group as-path

efc enable

efc filter 101 source