Configure ERSPAN with the Nexus 1000V

The Encapsulated Remote Switched Port Analyzer (ERSPAN) allows you to monitor traffic on multiple network interfaces or VLANs and then send the monitored traffic to one or more destinations. This guide explains how to configure ERSPAN on an installed ExtraHop appliance using the Nexus 1000V running on a Windows machine. The guide assumes experience using Cisco products.

To configure ERSPAN on an ExtraHop appliance, complete the following steps.

  1. Log in to the Admin UI (https://<extrahop_ip>/admin).

  2. Go to the Network Settings section and click Connectivity.

  3. Go to the Interface 1 section and click Change.

  4. On the Network Settings for Interface 1 page, click the Interface Mode drop-down list and select Management Port + RPCAP/ERSPAN Target.

  5. Complete the remaining fields and click Save.

  6. Depending on your configuration set or disable the remaining interfaces.

    For more information about setting up the network interfaces, refer to the Connectivitysection of the Admin UI Help.
  7. Log into your virtual supervisor module (VSM).

  8. Determine virtual Ethernet hosts that you want to monitor.

    Switch# Show int virt

  9. Enter config mode.

    Switch# config terminal

  10. Create new monitor session aka, a port mirroring session

    switch(config)# monitor session 1 type erspan-source

  11. Enter the ExtraHop ERSPAN target IP.

    switch(config-erspan-src)# destination ip

  12. Set an ERSPAN ID.

    switch(config-erspan-src)# erspan-id 1

  13. Set the MTU to 9000.

    switch(config-erspan-src)# mtu 9000

    To minimize the chance of drops, set the ERSPAN MTU as high as possible. On the Cisco Nexus 1000V, change the default MTU of 1500 to the current max of 9000. In addition, consider turning off TCP segmentation offloading on the operating systems involved in forwarded communication.
  14. Add data sources.

    1. The following example shows data being taken from a guest.

      switch(config-erspan-src)# source interface vethernet 3-5 both

      In this example, both means the VM is both sending and receiving data.

    2. The following example shows data being taken from all traffic received by the VLAN.

      switch(config-erspan-src)# source vlan 1010 rx

  15. Enable the monitoring session.

    switch(config-erspan-src)# no shut

  16. Exit from ERSPAN source to config mode.

    switch(config-erspan-src)# exit

  17. Exit config mode to the enable prompt

    switch(config)# exit

  18. Save your changes.

    switch# copy running-config startup-config

  19. Check the settings.

    switch# show monitor session 1

    A functioning monitoring session will look similar to this example.

  20. Log in to the ExtraHop Web UI (https://<extrahop_ip>/extrahop) to view monitored traffic.

  • Cisco: Configuring an ERSPAN Port Profile

  • ExtraHop: ExtraHop Admin UI Help

Published 2017-04-20 22:58