ERSPAN sessions allow you to monitor traffic on one or more ports, or one or more VLANs, and send the monitored traffic to one or more destination ports. ERSPAN sends traffic to a network analyzer such as a SwitchProbe device or other Remote Monitoring (RMON) probe. ERSPAN supports source ports, source VLANs, and destination ports on different routers, which provides remote monitoring of multiple routers across your network (see ).

ERSPAN consists of an ERSPAN source session, routable ERSPAN GRE-encapsulated traffic, and an ERSPAN destination session. You separately configure ERSPAN source sessions and destination sessions on different routers.

An ERSPAN source session is defined by the following:

• A session ID
• A list of source ports or source VLANs to be monitored by the session
• The destination and the origin IP addresses, which are used as the destination and source IP addresses of the GRE envelope for the captured traffic, respectively
• An ERSPAN flow ID
• Optional attributes related to the GRE envelope such as IP TOS and TTL.

For a source port or a source VLAN, the ERSPAN can monitor ingress, egress, or both ingress and egress traffic.

ERSPAN source sessions do not copy ERSPAN GRE-encapsulated traffic from source ports. Each ERSPAN source session can have either ports or VLANs as sources, but not both.

The ERSPAN source sessions copies traffic from the source ports or source VLANs and forwards the traffic using routable GRE-encapsulated packets to the ERSPAN destination session. The ERSPAN destination session switches the traffic to the destination ports.

Configure ERSPAN traffic on the Branch edge router. You must enable ERSPAN on both the WAN and LAN interface to provide visibility into traffic flows entering and leaving the branch.

Refer to “Configuring Local SPAN and ERSPAN” in the Cisco Nexus 1000V System Management Configuration Guide, Release 4.2(1) SV1(4)

You must configure ERSPAN on the Cisco Prime NAM VSB so that the Prime NAM receives data.

See the Sending ERSPAN Data Directly to the Cisco Prime NAM Management Interface about using ERSPAN as a data source:

Note	Depending on the NX-OS version on your managed device, the CLI format for configuring an ERSPAN session may be different than what appears in this document. For details on using ERSPAN as a data source, see your specific OS product documentation.

Configure NetFlow traffic on the Branch edge router. You must enable NetFlow on both the WAN and

LAN interface to provide visibility into traffic flows entering and leaving the branch.

config t
interface <interface>
		ip route-cache flow
		exit
ip flow-export version 5 
ip flow-export destination <NAM-Ip-Address> 3000

Note	The UDP port number must be set to 3000. You can change this using the NAM CLI. See the Cisco Prime Network Analysis Module Command Reference Guide

Also make sure the SNMP community string is configured on the device. Read Only or Read Write community string works.

snmp-server community <RO-string> RO

See the Customizing Cisco Prime NAM chapter in the Cisco Prime NAM User Guide available at http:/​/​www.cisco.com/​c/​en/​us/​support/​cloud-systems-management/​prime-network-analysis-module-software/​products-user-guide-list.html, for detailed procedures.

You can test the SNMP community strings for the devices in the Devices table. To test a device, select it from the Devices table under Setup > Traffic > NAM data Sources, then click Edit. Enter the parameters and click Test Connectivity.

1.    Choose Setup > Managed Device > Device Information.

2.    Click the Test Connectivity button to perform an SNMP test. Click Close when finished.

3.    Click Submit to submit the information and close the window.

Monitoring the managed device interfaces provides per-interface statistics directly from the Nexus switch. Go to the Analyze > Managed Device > Interfaces .

To change the interval, go to the Interactive Report on the left side of the screen and click the Filter button.