# Add Inline Interfaces for IPS engines

Define Inline Interfaces if you want to position a Single IPS or Inline IPS Cluster directly in the traffic path so that any traffic that is to be inspected goes through the IPS engine.

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Inline Interfaces allow traffic to flow through the IPS engine, so that traffic that is deemed harmful can be actively filtered out. An Inline Interface is configured with two Interface IDs, representing two physical interfaces or two VLANs. The IPS engine can inspect the traffic coming from one interface and either stop the traffic or send it out through the other interface. The two interfaces are equal in the configuration. Traffic that is allowed through is always forwarded from one interface to the other (there is no routing decision involved). Inline Interfaces do not have an IP address or a MAC address visible to the network.

Note: Some Forcepoint Network Security Platform appliances use a fail-open network card. Fail-open network cards have fixed pairs of ports. Take particular care to map these ports correctly. Otherwise, the network cards do not correctly fail open when the IPS engine is offline.

In addition to the Interface IDs, Inline Interfaces also have definitions for the corresponding Logical Interface that the interface belongs to. A single Logical Interface can represent one or more pairs of Inline Interfaces. The Logical Interface element can be used to represent the interfaces in the IPS Policy. You cannot select the same Logical Interface for a Capture Interface and an Inline Interface on the same IPS engine.

The number of Inline Interfaces you can configure is limited by the IPS engine’s license.

For more details about the product and how to configure features, click Help or press F1.

## Steps

1. Right-click a Single IPS or IPS Cluster and select Edit <element type>.
   The Engine Editor opens.
2. In the navigation pane on the left, select Interfaces.
   The Interfaces pane opens on the right.
3. Right-click the empty space, then select New Physical Interface.
4. Define the interface properties.
   Select Inline Interface as the interface Type.
   CAUTION:
   Using Bypass as the Failure Mode requires a fail-open network interface card. If the ports that represent the interfaces cannot fail open, policy installation fails on the Security Engine. Bypass mode is not compatible with VLAN retagging. In network environments where VLAN retagging is used, normal mode is automatically enforced.
5. Click OK to save the interface settings.
6. Continue the configuration in one of the following ways:
   - If you are creating an new IPS element, select system communication roles for IPS interfaces.
   - Otherwise, click Save and Refresh to activate the new interface configuration.

## Physical Interface Properties dialog box (IPS engine)

Use this dialog box to define the Physical Interface properties for a Single IPS engine, IPS Cluster, Virtual IPS engine, or Master Engine in the IPS role.

Note: The available options can vary depending on the type of IPS engine.

Option | Definition
--- | ---
General tab
Interface ID | The Interface ID automatically maps to a physical network port of the same number during the initial configuration of the Engine. The mapping can be changed as necessary through command-line tools. Note: For Master Engines, changes to the interface mapping do not affect the Interface IDs that are defined for Virtual Engines in Virtual Resource elements.
Type | Normal Interface — Corresponds to a single network interface on the engine. Not supported on Virtual IPS engines. Capture Interface — Network traffic is monitored only. Traffic cannot be blocked. Inline Interface — The interface is directly on the traffic path so that traffic must always pass through the engine to reach its destination. Only traffic that attempts to pass through Inline Interfaces can be actively filtered.
Zone (Optional) | Select the network zone to which the interface belongs. Click Select to select an element, or click New to create an element.
MTU (Optional) | The maximum transmission unit (MTU) size on the connected link. Either enter a value between 400–65535 or select a common MTU value from the list. If the interface is a Physical Interface, the same MTU is automatically applied to any VLANs created under it. The default value (also the maximum standard MTU in Ethernet) is 1500. Do not set a value larger than the standard MTU, unless you know that all devices along the communication path support it. To set the MTU for a Virtual Engine, you must configure the MTU for the interface on the Master Engine that hosts the Virtual Engine, then refresh the policy on the Master Engine and the Virtual Engine.
Comment (Optional) | A comment for your own reference.

Option | Definition
--- | ---
Inline Interface Settings or Capture Interface Settings section
Reset Interface | (When Type is Capture Interface) Select the Reset Interface to specify the interface through which TCP connection resets are sent when Reset responses are used in your policy.
Logical Interface | Specifies the Logical Interface. You cannot use the same Logical Interface element for both Inline and Capture Interfaces on the same Virtual Engine.
Failure Mode | (When Type is Inline Interface) Select how traffic to the Inline Interface is handled if the engine goes offline. Bypass — traffic is allowed through the Inline Interface without inspection. Normal — traffic is not allowed through the Inline Interface. Note: If there are VLAN Interfaces under the Inline Interface, you must select Bypass. Note: For Virtual Engines, this option is set on the Master Engine. CAUTION: Using bypass mode requires a fail-open network interface card. If the ports that represent the interfaces cannot fail open, policy installation fails on the Security Engine. Bypass mode is not compatible with VLAN retagging. In network environments where VLAN retagging is used, normal mode is automatically enforced.
Inspect unspecified VLANs | (When Type is Capture Interface or Inline Interface) Select this option to make the engine inspect traffic from VLANs that are not included in the engine’s interface configuration. We recommend that you keep this option selected if you do not have a specific reason to deselect it.
Inspect QinQ | Select this option to make the engine inspect double-tagged VLAN traffic as defined in IEEE 802.1Q. We recommend that you keep this option selected if you do not have a specific reason to deselect it.
Bypass unspecified VLANs (Master Engines only) | (When Type is Inline Interface) When this option is selected, traffic from VLANs that are not allocated to any Virtual Engine is bypassed without inspection. Deselect this option to make the Master Engine block traffic from VLANs that are not allocated to any Virtual Engine. We recommend that you keep this option selected if you do not have a specific reason to deselect it.

Option | Definition
--- | ---
Second Interface section (When Type is Inline Interface)
ID | Select a Second Interface ID. The Interface ID is mapped to a physical network port of the same number during the initial configuration of the engine.
Zone (Optional) | Select the network zone to which the interface belongs. Click Select to select an element, or click New to create an element.
Second Interface ID (Master Engines only) | Select a Second Interface ID. The Interface ID is mapped to a physical network port of the same number during the initial configuration of the engine.

Option | Definition
--- | ---
QoS Mode (Optional) | Select the QoS mode to apply to the link on this interface. You can select from one of the following options: No QoS: When selected, no QoS mode is enabled. QoS Statistics Only: It allows the collection of QoS Class-based counters without activating any other QoS feature. DSCP Handling and Throttling: When selected, no queues and no throttling of all traffic. Only the connections that are tagged with QoS Class are treated as per the action that is defined in the QoS policy. Full QoS: It throttles all traffic to the Interface Throughput Limit that is set in the interface properties Note: If Full QoS or DSCP Handling and Throttling is selected, a QoS policy must also be selected. If Full QoS is selected, the throughput must also be defined. If the interface is a Physical Interface, the same QoS mode is automatically applied to any VLANs created under it.
QoS Policy | (When QoS Mode is Full QoS or DSCP Handling and Throttling) The QoS policy for the link on this interface. If the interface is a Physical Interface, the same QoS policy is automatically selected for any VLANs created under it. Note: If a Virtual Resource has a throughput limit defined, the interfaces on the Virtual Engine that use a QoS policy all use the same policy. The policy used in the first interface is used for all the interfaces.
Interface Throughput Limit | (When QoS Mode is Full QoS) Enter the throughput for the link on this interface as megabits per second. If the interface is a Physical Interface, the same throughput is automatically applied to any VLANs created under it. The throughput is for uplink speed (outgoing traffic) and typically must correspond to the speed of an Internet link (such as an ADSL line), or the combined speeds of several such links when connected to a single interface. CAUTION: Make sure that you set the interface speed correctly. When the bandwidth is set, the Engine always scales the total amount of traffic on this interface to the bandwidth you defined. This scaling happens even if there are no bandwidth limits or guarantees defined for any traffic. CAUTION: The throughput for a Physical Interface for a Virtual Engine must not be higher than the throughput for the Master Engine interface that hosts the Virtual Engine. Contact the administrator of the Master Engine before changing this setting.

Option | Definition
--- | ---
Virtual Resource section (Master Engines only)
Virtual Resource | The Virtual Resource associated with the interface. Select the same Virtual Resource in the properties of the Virtual Engine to add the Virtual Engine to the Master Engine. If the interface is to be used for the Master Engine system communications, select None. For Master Engines that host Virtual Engines, you can select Multiple Virtual Resources to allow several Virtual Engines to share a single physical interface. To add multiple Virtual Resources for Virtual IPS engines or Virtual Layer 2 Engines, add VLAN Interfaces to the Physical Interface, then select a Virtual Resource in the properties of each VLAN Interface.
Allow VLAN Definition in Virtual Engine | (When the Virtual Resource option is a single Virtual Resource) When selected, you can add VLAN Interfaces to the automatically created physical interfaces in the Virtual Security Engines that are associated with this interface.
Virtual Engine Interface ID | (When the Virtual Resource option is a single Virtual Resource) Specifies the Interface ID of the Physical Interface in the Virtual Engine that is associated with this interface.

Option | Definition
--- | ---
Advanced tab (All optional settings)
Override Engine's Default Settings | When selected, the default settings of the Security Engine are overridden.
SYN Rate Limits | Default — The interface uses the SYN rate limits defined for the Security Engine on the Advanced Settings branch of the Engine Editor. None — Disables SYN rate limits on the interface. Automatic — This is the recommended mode if you want to override the general SYN rate limits defined on the Advanced Settings branch of the Engine Editor. The Engine calculates the number of allowed SYN packets per second and the burst size (the number of allowed SYNs before the Security Engine starts limiting the SYN rate) based on the Engine’s capacity and memory size. Custom — Enter the values for Allowed SYNs per Second and Burst Size.
Allowed SYNs per Second | Defines the number of allowed SYN packets per second.
Burst Size | The number of allowed SYNs before the Engine starts limiting the SYN rate. We recommend that you set the burst size to be at least one tenth of the Allowed SYNs per Second value. If the burst size is too small, SYN rate limits do not work. For example, if the value for Allowed SYNs per Second is 10000, set the value for Burst Size to at least 1000.
Enable Log Compression | By default, each generated Antispoofing and Discard log entry is logged separately and displayed as a separate entry in the Logs view. Log Compression settings allow you to define the maximum number of separately logged entries. When the defined limit is reached, a single antispoofing log entry or Discard log entry is logged. The single entry contains information about the total number of the generated Antispoofing log entries or Discard log entries. After this log entry, the logging returns to normal and all generated entries are once more logged and displayed separately. Log Compression is useful when the routing configuration generates a large volume of antispoofing logs or the number of Discard logs becomes high. For each event type, Antispoofing or Discard, you can define: Log Rate (Entries/s) — The maximum number of entries per second. The default value for antispoofing entries is 100 entries/s. By default, Discard log entries are not compressed. Burst Size (Entries) — The maximum number of matching entries in a single burst. The default value for antispoofing entries is 1000 entries. By default, Discard log entries are not compressed.
Set to Default | Returns all changes to the log compression settings to the default settings.