Configure a Passive Interface

This section describes how to:

  • Enable the interface. By default, interfaces are disabled.

  • Set the interface mode to Passive or ERSPAN. For ERSPAN interfaces, you will set the ERSPAN parameters and the IP address.

  • Change the MTU. By default, the MTU is set to 1500 bytes. For more information about the MTU, see About the MTU.

  • Set a specific speed and duplex (if available). By default, speed and duplex are set to Auto.

Note

For the Secure Firewall Threat Defense on the FXOS chassis, you configure basic interface settings on the Firepower 4100/9300. See Configure a Physical Interface for more information.

Before you begin

Procedure

Step 1

Select Devices > Device Management and click Edit (edit icon) for your threat defense device. The Interfaces page is selected by default.

Step 2

Click Edit (edit icon) for the interface you want to edit.

Step 3

In the Mode drop-down list, choose Passive or Erspan.

Step 4

Enable the interface by checking the Enabled check box.

Step 5

In the Name field, enter a name up to 48 characters in length.

Step 6

From the Security Zone drop-down list, choose a security zone or add a new one by clicking New.

Step 7

(Optional) Add a description in the Description field.

The description can be up to 200 characters on a single line, without carriage returns.

Step 8

(Optional) On General, set the MTU between 64 and 9198 bytes; for the Secure Firewall Threat Defense Virtual and Secure Firewall Threat Defense on the FXOS chassis, the maximum is 9000 bytes.

The default is 1500 bytes.

Step 9

For ERSPAN interfaces, set the following parameters:

  • Flow Id—Configure the ID used by the source and destination sessions to identify the ERSPAN traffic, between 1 and 1023. This ID must also be entered in the ERSPAN destination session configuration.

  • Source IP—Configure the IP address used as the source of the ERSPAN traffic.

Step 10

For ERSPAN interfaces, set the IPv4 address and mask on IPv4.

Step 11

(Optional) Set the duplex and speed by clicking Hardware Configuration.

The exact speed and duplex options depend on your hardware.

  • Duplex—Choose Full, Half, or Auto. Auto is the default.

  • Speed—Choose 10, 100, 1000, or Auto. Auto is the default.

Step 12

Click OK.

Step 13

Click Save.

You can now go to Deploy > Deployment and deploy the policy to assigned devices. The changes are not active until you deploy them.