Add Capture Interfaces for Layer 2 Firewalls

Capture Interfaces listen to traffic that is not routed through the Layer 2 Firewall.

You can have as many Capture Interfaces as there are available physical ports on the Layer 2 Firewall engine. External equipment must be set up to mirror traffic to the Capture Interface.

Capture Interfaces are used to configure a Layer 2 Firewall in Passive Firewall mode. In Passive Firewall mode, the Layer 2 Firewall only listens to traffic that does not flow through it.

Capture Interfaces have definitions for the corresponding Logical Interface that the interface belongs to. The Logical Interface represents one or more network interfaces that capture the traffic for inspection. Each Capture Interface is bound to one Logical Interface. More than one Capture Interface can optionally be bound to the same Logical Interface.

You cannot select the same Logical Interface for a Capture Interface and an Inline Interface on the same Layer 2 Firewall.

A Reset Interface can be selected for a Capture Interface to send TCP Reset responses for the traffic captured from the interface. The Reset Interface is a Normal Interface that can reach the communicating components with a TCP Reset (for example, a Normal Interface connected to the monitored network).

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

Steps

  1. Right-click a Single Layer 2 Firewall or Layer 2 Firewall 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 and select New Physical Interface.
  4. Define the interface properties.
    Note: Select Capture Interface as the interface Type.
  5. Click OK to save the interface settings.
  6. Continue the configuration in one of the following ways:
    • If you are creating a new Layer 2 Firewall element, select system communication roles for Layer 2 Firewall interfaces.
    • If you added an interface to an existing Layer 2 Firewall element, click Save and Refresh to activate the new interface configuration.

Physical Interface Properties dialog box (Layer 2 Firewall)

Use this dialog box to define the Physical Interface properties for a Single Layer 2 Firewall, Layer 2 Firewall Cluster, Virtual Layer 2 Firewall, or Master NGFW Engine in the Layer 2 Firewall role.

Note: The available options can vary depending on the type of Layer 2 Firewall.
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 the engine’s command line interface.
Note: Changes to the Master NGFW Engine interface mapping do not affect the Interface IDs that are defined for Virtual NGFW Engines in Virtual Resource elements.
Type
  • Normal interface — Corresponds to a single network interface on the Layer 2 Firewall engine.
  • Capture Interface — Traffic is only captured for inspection.
    Note: Capture Interfaces allow the hosted Virtual Layer 2 Firewall to listen to traffic that is not routed through the Master NGFW Engine. You can have as many Capture Interfaces as there are available physical ports on the Master NGFW Engine. External equipment must be set up to mirror traffic to the Capture Interface.
  • Inline Interface — The interface is directly on the traffic path so that traffic must always pass through the Layer 2 Firewall to reach its destination. Only traffic that attempts to pass through Inline Interfaces can be actively filtered.
    Note: An Inline Interface consists of two different Physical Interfaces on the Master NGFW Engine. This way, the hosted Virtual Layer 2 Firewall can inspect the traffic coming from one interface and either stop the traffic or send it out through the other interface.
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 NGFW Engine, you must configure the MTU for the interface on the Master NGFW Engine that hosts the Virtual NGFW Engine, then refresh the policy on the Master NGFW Engine and the Virtual NGFW 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 NGFW Engine.
Inspect unspecified VLANs

(When Type is Capture Interface or Inline Interface)

Deselect this option to make the NGFW Engine ignore traffic from VLANs that are not included in the NGFW 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 NGFW Engines only)

(When Type is Inline Interface)

When this option is selected, traffic from VLANs that are not allocated to any Virtual NGFW Engine is bypassed without inspection. Deselect this option to make the Master NGFW Engine block traffic from VLANs that are not allocated to any Virtual NGFW 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

(Inline Interfaces only)

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.
Note: Select the Second Interface ID of the Inline Interface in the Virtual Layer 2 Firewall that is associated with this interface.
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 NGFW Engines only)

(When Type is Inline Interface)

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)

Defines how QoS is applied to the link on this interface.

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 NGFW 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 NGFW 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 NGFW Engine must not be higher than the throughput for the Master NGFW Engine interface that hosts the Virtual NGFW Engine. Contact the administrator of the Master NGFW Engine before changing this setting.
Option Definition
Virtual Resource section

(Master NGFW Engines only)

Virtual Resource The Virtual Resource associated with the interface. Select the same Virtual Resource in the properties of the Virtual Firewall element to add the Virtual NGFW Engine to the Master NGFW Engine.

Only one Virtual Resource can be selected for each Physical Interface. If you want to add multiple Virtual Resources, add VLAN Interfaces to the Physical Interface, then select the Virtual Resource in the VLAN Interface properties.

Allow VLAN Definition in Virtual Engine When selected, allows VLAN Interfaces to be added to the automatically created Physical Interfaces in the Virtual NGFW Engine that is associated with this interface.
Virtual Engine Interface ID Specifies the Interface ID of the Physical Interface in the Virtual NGFW Engine that is associated with this interface.
Option Definition
Advanced tab

(All optional settings)

Note: These options cannot be selected if using Capture Interfaces.
Override Engine's Default Settings When selected, the default settings of the NGFW Engine are overridden.
SYN Rate Limits
  • Default — The interface uses the SYN rate limits defined for the NGFW 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 NGFW Engine calculates the number of allowed SYN packets per second and the burst size (the number of allowed SYNs before the NGFW Engine starts limiting the SYN rate) based on the NGFW 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 NGFW 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.