Firepower Management Center Configuration Guide, Version 6.1

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Book Title

Firepower Management Center Configuration Guide, Version 6.1

Chapter Title

Regular Firewall Interfaces for Firepower Threat Defense

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Updated:
August 15, 2016

Chapter: Regular Firewall Interfaces for Firepower Threat Defense

Regular Firewall Interfaces for Firepower Threat Defense

This chapter includes regular firewall FTD interface configuration including EtherChannels, VLAN subinterfaces, IP addressing, and more.


Note

For initial interface configuration on the Firepower 4100/9300, see Configure Interfaces.

Configure EtherChannel and Redundant Interfaces

This section tells how to configure EtherChannels and redundant interfaces.


Note

For the Firepower 4100/9300, you configure EtherChannels in FXOS. See Add an EtherChannel (Port Channel) for more information.


Note

Only ASA 5500-X models support redundant interfaces; Firepower models do not support them.

About EtherChannels and Redundant Interfaces

This section describes EtherChannels and Redundant Interfaces.

About Redundant Interfaces (ASA Platform Only)

A logical redundant interface consists of a pair of physical interfaces: an active and a standby interface. When the active interface fails, the standby interface becomes active and starts passing traffic. You can configure a redundant interface to increase the Firepower Threat Defense device reliability.

You can configure up to 8 redundant interface pairs.

Redundant Interface MAC Address

The redundant interface uses the MAC address of the first physical interface that you add. If you change the order of the member interfaces in the configuration, then the MAC address changes to match the MAC address of the interface that is now listed first. Alternatively, you can assign a manual MAC address to the redundant interface, which is used regardless of the member interface MAC addresses. When the active interface fails over to the standby, the same MAC address is maintained so that traffic is not disrupted.

About EtherChannels

An 802.3ad EtherChannel is a logical interface (called a port-channel interface) consisting of a bundle of individual Ethernet links (a channel group) so that you increase the bandwidth for a single network. A port channel interface is used in the same way as a physical interface when you configure interface-related features.

You can configure up to 48 EtherChannels, depending on how many interfaces your model supports.

Channel Group Interfaces

Each channel group can have up to 16 active interfaces. For switches that support only 8 active interfaces, you can assign up to 16 interfaces to a channel group: while only 8 interfaces can be active, the remaining interfaces can act as standby links in case of interface failure. For 16 active interfaces, be sure that your switch supports the feature (for example, the Cisco Nexus 7000 with F2-Series 10 Gigabit Ethernet Module).

All interfaces in the channel group must be the same type and speed. The first interface added to the channel group determines the correct type and speed.

The EtherChannel aggregates the traffic across all the available active interfaces in the channel. The interface is selected using a proprietary hash algorithm, based on source or destination MAC addresses, IP addresses, TCP and UDP port numbers and VLAN numbers.

Connecting to an EtherChannel on Another Device

The device to which you connect the FTD EtherChannel must also support 802.3ad EtherChannels; for example, you can connect to the Catalyst 6500 switch or the Cisco Nexus 7000.

When the switch is part of a Virtual Switching System (VSS) or Virtual Port Channel (vPC), then you can connect FTD interfaces within the same EtherChannel to separate switches in the VSS/vPC. The switch interfaces are members of the same EtherChannel port-channel interface, because the separate switches act like a single switch.

Figure 1. Connecting to a VSS/vPC

If you use the FTD in an Active/Standby failover deployment, then you need to create separate EtherChannels on the switches in the VSS/vPC, one for each FTD. On each FTD, a single EtherChannel connects to both switches. Even if you could group all switch interfaces into a single EtherChannel connecting to both FTD (in this case, the EtherChannel will not be established because of the separate FTD system IDs), a single EtherChannel would not be desirable because you do not want traffic sent to the standby FTD.

Figure 2. Active/Standby Failover and VSS/vPC
Link Aggregation Control Protocol

The Link Aggregation Control Protocol (LACP) aggregates interfaces by exchanging the Link Aggregation Control Protocol Data Units (LACPDUs) between two network devices.

You can configure each physical interface in an EtherChannel to be:

  • Active—Sends and receives LACP updates. An active EtherChannel can establish connectivity with either an active or a passive EtherChannel. You should use the active mode unless you need to minimize the amount of LACP traffic.

  • Passive—Receives LACP updates. A passive EtherChannel can only establish connectivity with an active EtherChannel. Not supported on Firepower hardware models.

  • On—The EtherChannel is always on, and LACP is not used. An “on” EtherChannel can only establish a connection with another “on” EtherChannel. Not supported on Firepower hardware models.

LACP coordinates the automatic addition and deletion of links to the EtherChannel without user intervention. It also handles misconfigurations and checks that both ends of member interfaces are connected to the correct channel group. “On” mode cannot use standby interfaces in the channel group when an interface goes down, and the connectivity and configurations are not checked.

Load Balancing

The FTD distributes packets to the interfaces in the EtherChannel by hashing the source and destination IP address of the packet (this criteria is configurable). The resulting hash is divided by the number of active links in a modulo operation where the resulting remainder determines which interface owns the flow. All packets with a hash_value mod active_links result of 0 go to the first interface in the EtherChannel, packets with a result of 1 go to the second interface, packets with a result of 2 go to the third interface, and so on. For example, if you have 15 active links, then the modulo operation provides values from 0 to 14. For 6 active links, the values are 0 to 5, and so on.

If an active interface goes down and is not replaced by a standby interface, then traffic is rebalanced between the remaining links. The failure is masked from both Spanning Tree at Layer 2 and the routing table at Layer 3, so the switchover is transparent to other network devices.

EtherChannel MAC Address

All interfaces that are part of the channel group share the same MAC address. This feature makes the EtherChannel transparent to network applications and users, because they only see the one logical connection; they have no knowledge of the individual links.

The port-channel interface uses the lowest numbered channel group interface MAC address as the port-channel MAC address. Alternatively you can manually configure a MAC address for the port-channel interface. We recommend manually configuring a unique MAC address in case the group channel interface membership changes. If you remove the interface that was providing the port-channel MAC address, then the port-channel MAC address changes to the next lowest numbered interface, thus causing traffic disruption.

Guidelines for EtherChannels and Redundant Interfaces

High Availability

  • When you use a redundant or EtherChannel interface as a High Availability link, it must be pre-configured on both units in the High Availability pair; you cannot configure it on the primary unit and expect it to replicate to the secondary unit because the High Availability link itself is required for replication.

  • If you use a redundant or EtherChannel interface for the state link, no special configuration is required; the configuration can replicate from the primary unit as normal. For the Firepower 4100/9300 chassis, all interfaces, including EtherChannels, need to be pre-configured on both units.

  • You can monitor redundant or EtherChannel interfaces for High Availability. When an active member interface fails over to a standby interface, this activity does not cause the redundant or EtherChannel interface to appear to be failed when being monitored for device-level High Availability. Only when all physical interfaces fail does the redundant or EtherChannel interface appear to be failed (for an EtherChannel interface, the number of member interfaces allowed to fail is configurable).

  • If you use an EtherChannel interface for a High Availability or state link, then to prevent out-of-order packets, only one interface in the EtherChannel is used. If that interface fails, then the next interface in the EtherChannel is used. You cannot alter the EtherChannel configuration while it is in use as a High Availability link. To alter the configuration, you need to temporarily disable High Availability, which prevents High Availability from occurring for the duration.

Model Support

  • You cannot add EtherChannels in FMC for the Firepower 4100/9300 or FTDv. The Firepower 4100/9300 supports EtherChannels, but you must perform all hardware configuration of EtherChannels in FXOS on the chassis.

  • Redundant interfaces are only supported on the ASA 5500-X platform; they are not supported on the Firepower 4100/9300 chassis, FTDv, .

General Redundant Interface Guidelines

  • You can configure up to 8 redundant interface pairs.

  • All FTD configuration refers to the logical redundant interface instead of the member physical interfaces.

  • You cannot use a redundant interface as part of an EtherChannel, nor can you use an EtherChannel as part of a redundant interface. You cannot use the same physical interfaces in a redundant interface and an EtherChannel interface. You can, however, configure both types on the FTD if they do not use the same physical interfaces.

  • If you shut down the active interface, then the standby interface becomes active.

  • Redundant interfaces do not support Diagnostic slot/port interfaces as members. You can, however, set a redundant interface comprised of non-Diagnostic interfaces as management-only.

General EtherChannel Guidelines

  • You can configure up to 48 EtherChannels, depending on how many interfaces are available on your model.

  • Each channel group can have up to 16 active interfaces. For switches that support only 8 active interfaces, you can assign up to 16 interfaces to a channel group: while only 8 interfaces can be active, the remaining interfaces can act as standby links in case of interface failure. For 16 active interfaces, be sure that your switch supports the feature (for example, the Cisco Nexus 7000 with F2-Series 10 Gigabit Ethernet Module).

  • All interfaces in the channel group must be the same type and speed. The first interface added to the channel group determines the correct type and speed.

  • The device to which you connect the FTD EtherChannel must also support 802.3ad EtherChannels.

  • The FTD does not support LACPDUs that are VLAN-tagged. If you enable native VLAN tagging on the neighboring switch using the Cisco IOS vlan dot1Q tag native command, then the FTD will drop the tagged LACPDUs. Be sure to disable native VLAN tagging on the neighboring switch.

  • ASA 5500-X models do not support LACP rate fast; LACP always uses the normal rate. This setting is not configurable. Note that the Firepower 4100/9300, which configures EtherChannels in FXOS, has the LACP rate set to fast by default; on these platforms, the rate is configurable.

  • In Cisco IOS software versions earlier than 15.1(1)S2, the FTD did not support connecting an EtherChannel to a switch stack. With default switch settings, if the FTD EtherChannel is connected cross stack, and if the master switch is powered down, then the EtherChannel connected to the remaining switch will not come up. To improve compatibility, set the stack-mac persistent timer command to a large enough value to account for reload time; for example, 8 minutes or 0 for indefinite. Or, you can upgrade to more a more stable switch software version, such as 15.1(1)S2.

  • All FTD configuration refers to the logical EtherChannel interface instead of the member physical interfaces.

  • You cannot use a redundant interface as part of an EtherChannel, nor can you use an EtherChannel as part of a redundant interface. You cannot use the same physical interfaces in a redundant interface and an EtherChannel interface. You can, however, configure both types on the FTD if they do not use the same physical interfaces.

Configure a Redundant Interface (ASA Platform Only)

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

A logical redundant interface consists of a pair of physical interfaces: an active and a standby interface. When the active interface fails, the standby interface becomes active and starts passing traffic. You can configure a redundant interface to increase the FTD reliability. By default, redundant interfaces are enabled.

  • You can configure up to 8 redundant interface pairs.

  • Both member interfaces must be of the same physical type. For example, both must be GigabitEthernet.


Note

Redundant interfaces are not supported on the Firepower platform; only ASA 5500-X models support redundant interfaces.

Before you begin

  • You cannot add a physical interface to the redundant interface if you configured a name for it. You must first remove the name.


    Caution

    If you are using a physical interface already in your configuration, removing the name will clear any configuration that refers to the interface.

Procedure

Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

Enable the member interfaces according to Enable the Physical Interface and Configure Ethernet Settings.

Step 3

Click Add Interfaces > Redundant Interface.

Step 4

On the General tab, set the following parameters:

  1. Redundant ID—Set an integer between 1 and 8.

  2. Primary Interface—Choose an interface from the drop-down list. After you add the interface, any configuration for it (such as an IP address) is removed.

  3. Secondary Interface—The second interface must be the same physical type as the first interface.

Step 5

Click OK.

Step 6

Click Save.

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

Step 7

(Optional) Add a VLAN subinterface. See Add a Subinterface.

Step 8

Configure the routed or transparent mode interface parameters. See Configure Routed Mode Interfaces or Configure Transparent Mode Bridge Group Interfaces.

Configure an EtherChannel

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

This section describes how to create an EtherChannel port-channel interface, assign interfaces to the EtherChannel, and customize the EtherChannel.

Guidelines

  • You can configure up to 48 EtherChannels, depending on the number of interfaces for your model.

  • Each channel group can have up to 16 active interfaces. For switches that support only 8 active interfaces, you can assign up to 16 interfaces to a channel group: while only 8 interfaces can be active, the remaining interfaces can act as standby links in case of interface failure.

  • All interfaces in the channel group must be the same type, speed, and duplex. Half duplex is not supported.


Note

For the Firepower 4100/9300, you configure EtherChannels in FXOS. See Add an EtherChannel (Port Channel) for more information.

Before you begin

  • You cannot add a physical interface to the channel group if you configured a name for it. You must first remove the name.


    Note

    If you are using a physical interface already in your configuration, removing the name will clear any configuration that refers to the interface.

Procedure

Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

Enable the member interfaces according to Enable the Physical Interface and Configure Ethernet Settings.

Step 3

Click Add Interfaces > Ether Channel Interface.

Step 4

On the General tab, set the Ether Channel ID to a number between 1 and 48.

Step 5

In the Available Interfaces area, click an interface and then click Add to move it to the Selected Interfaces area. Repeat for all interfaces that you want to make members.

Make sure all interfaces are the same type and speed. The first interface you add determines the type and speed of the EtherChannel. Any non-matching interfaces you add will be put into a suspended state. The FMC does not prevent you from adding non-matching interfaces.

Step 6

(Optional) Click the Advanced tab to customize the EtherChannel. Set the following parameters on the Information sub-tab:

  • Load Balancing—Select the criteria used to load balance the packets across the group channel interfaces. By default, the FTD device balances the packet load on interfaces according to the source and destination IP address of the packet. If you want to change the properties on which the packet is categorized, choose a different set of criteria. For example, if your traffic is biased heavily towards the same source and destination IP addresses, then the traffic assignment to interfaces in the EtherChannel will be unbalanced. Changing to a different algorithm can result in more evenly distributed traffic. For more information about load balancing, see Load Balancing.

  • LACP Mode—Choose Active, Passive, or On. We recommend using Active mode (the default).

  • Active Physical Interface: Range—From the left drop-down list, choose the minimum number of active interfaces required for the EtherChannel to be active, between 1 and 16. The default is 1. From the right drop-down list, choose the maximum number of active interfaces allowed in the EtherChannel, between 1 and 16. The default is 16. If your switch does not support 16 active interfaces, be sure to set this command to 8 or fewer.

  • Active Mac Address—Set a manual MAC address if desired. The mac_address is in H.H.H format, where H is a 16-bit hexadecimal digit. For example, the MAC address 00-0C-F1-42-4C-DE is entered as 000C.F142.4CDE.

Step 7

(Optional) Click the Hardware Configuration tab and set the Duplex and Speed to override these settings for all member interfaces. This method provides a shortcut to set these parameters because these parameters must match for all interfaces in the channel group.

Step 8

Click OK.

Step 9

Click Save.

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

Step 10

(Optional) Add a VLAN subinterface. See Add a Subinterface.

Step 11

Configure the routed or transparent mode interface parameters. See Configure Routed Mode Interfaces or Configure Transparent Mode Bridge Group Interfaces.

Configure VLAN Subinterfaces and 802.1Q Trunking

VLAN subinterfaces let you divide a physical, redundant, or EtherChannel interface into multiple logical interfaces that are tagged with different VLAN IDs. An interface with one or more VLAN subinterfaces is automatically configured as an 802.1Q trunk. Because VLANs let you keep traffic separate on a given physical interface, you can increase the number of interfaces available to your network without adding additional physical interfaces or devices.

Guidelines and Limitations for VLAN Subinterfaces

High Availability

You cannot use a subinterface for the failover or state link.

Additional Guidelines

  • Preventing untagged packets on the physical interface—If you use subinterfaces, you typically do not also want the physical interface to pass traffic, because the physical interface passes untagged packets. This property is also true for the active physical interface in a redundant interface pair and for EtherChannel links. Because the physical, redundant, or EtherChannel interface must be enabled for the subinterface to pass traffic, ensure that the physical, redundant, or EtherChannel interface does not pass traffic by not configuring a name for the interface. If you want to let the physical, redundant, or EtherChannel interface pass untagged packets, you can configure the name as usual.

  • You cannot configure subinterfaces on the Diagnostic interface.

  • The FTD does not support the Dynamic Trunking Protocol (DTP), so you must configure the connected switch port to trunk unconditionally.

  • You might want to assign unique MAC addresses to subinterfaces defined on the FTD, because they use the same burned-in MAC address of the parent interface. For example, your service provider might perform access control based on the MAC address. Also, because IPv6 link-local addresses are generated based on the MAC address, assigning unique MAC addresses to subinterfaces allows for unique IPv6 link-local addresses, which can avoid traffic disruption in certain instances on the FTD.

Maximum Number of VLAN Subinterfaces by Device Model

The device model limits the maximum number of VLAN subinterfaces that you can configure. Note that you can configure subinterfaces on data interfaces only, you cannot configure them on the management interface.

The following table explains the limits for each device model.

Model

Maximum VLAN Subinterfaces

Firepower 4100

1024

Firepower 9300

1024

Firepower Threat Defense Virtual

50

ASA 5506-X



ASA 5506W-X

ASA 5506H-X

30

ASA 5508-X

50

ASA 5512-X

100

ASA 5515-X

100

ASA 5516-X

100

ASA 5525-X

200

ASA 5545-X

300

ASA 5555-X

500

Add a Subinterface

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

Add one or more subinterfaces to a physical, redundant, or port-channel interface.


Note

The parent physical interface passes untagged packets. You may not want to pass untagged packets, so be sure not to include the parent interface in your security policy.

Procedure

Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

Enable the parent interface according to Enable the Physical Interface and Configure Ethernet Settings.

Step 3

Click Add Interfaces > Sub Interface.

Step 4

On General, set the following parameters:

  1. Interface—Choose the physical, redundant, or port-channel interface to which you want to add the subinterface.

  2. Sub-Interface ID—Enter the subinterface ID as an integer between 1 and 4294967295. The number of subinterfaces allowed depends on your platform. You cannot change the ID after you set it.

  3. VLAN ID—Enter the VLAN ID between 1 and 4094 that will be used to tag the packets on this subinterface.

    This VLAN ID must be unique.
Step 5

Click OK.

Step 6

Click Save.

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

Step 7

Configure the routed or transparent mode interface parameters. See Configure Routed Mode Interfaces or Configure Transparent Mode Bridge Group Interfaces.

Configure Routed and Transparent Mode Interfaces

This section includes tasks to complete the regular interface configuration for all models in routed or transparent firewall mode.

About Routed and Transparent Mode Interfaces

The Firepower Threat Defense device supports two types of interfaces: routed and bridged.

Each Layer 3 routed interface requires an IP address on a unique subnet.

Bridged interfaces belong to a bridge group, and all interfaces are on the same network. The bridge group is represented by a Bridge Virtual Interface (BVI) that has an IP address on the bridge network. Routed mode only supports routed interfaces. Transparent firewall mode only supports bridge group and BVI interfaces.

Routed Mode Deployment

We recommend that you do not configure an IP address for the Diagnostic interface if you do not have an inside router. The benefit to leaving the IP address off of the Diagnostic interface is that you can place the Management interface on the same network as any other data interfaces. If you configure the Diagnostic interface, its IP address is typically on the same network as the Management IP address, and it counts as a regular interface that cannot be on the same network as any other data interfaces. Because the Management interface requires Internet access for updates, putting Management on the same network as an inside interface means you can deploy the FTD device with only a switch on the inside and point to the inside interface as its gateway. See the following deployment that uses an inside switch:



To cable the above scenario on the ASA 5506-X, ASA 5508-X, or ASA 5516-X, see the following:

If you configure the Diagnostic IP address, then you need an inside router:



Transparent Mode Deployment

Like the routed mode deployment, you can choose to deploy the device with an inside switch, in which case you need to keep the Diagnostic interface without an IP address:

Or you can deploy with an inside router, in which case you can use the Diagnostic interface with an IP address for additional management access:

Dual IP Stack (IPv4 and IPv6)

The Firepower Threat Defense device supports both IPv6 and IPv4 addresses on an interface. Make sure you configure a default route for both IPv4 and IPv6.

Guidelines and Requirements for Routed and Transparent Mode Interfaces

High Availability

  • Do not configure failover links with the procedures in this chapter. See the High Availability chapter for more information.

  • When you use High Availability, you must set the IP address and standby address for data interfaces manually; DHCP and PPPoE are not supported. Set the standby IP addresses on the Devices > Device Management > High Availability tab in the Monitored Interfaces area. See the High Availability chapter for more information.

IPv6

  • IPv6 is supported on all interfaces.

  • You can only configure IPv6 addresses manually in transparent mode.

  • The Firepower Threat Defense device does not support IPv6 anycast addresses.

Transparent Mode and Bridge Group Guidelines

  • You can create up to 250 bridge groups, with 4 interfaces per bridge group.

  • Each directly-connected network must be on the same subnet.

  • The Firepower Threat Defense device does not support traffic on secondary networks; only traffic on the same network as the BVI IP address is supported.

  • For IPv4, an IP address for the BVI is required for each bridge group for both management traffic and for traffic to pass through the Firepower Threat Defense device. IPv6 addresses are supported, but not required for the BVI.

  • You can only configure IPv6 addresses manually.

  • The BVI IP address must be on the same subnet as the connected network. You cannot set the subnet to a host subnet (255.255.255.255).

  • Management interfaces are not supported as bridge group members.

  • In transparent mode, you must use at least 1 bridge group; data interfaces must belong to a bridge group.

  • In transparent mode, do not specify the BVI IP address as the default gateway for connected devices; devices need to specify the router on the other side of the Firepower Threat Defense device as the default gateway.

  • In transparent mode, the default route, which is required to provide a return path for management traffic, is only applied to management traffic from one bridge group network. This is because the default route specifies an interface in the bridge group as well as the router IP address on the bridge group network, and you can only define one default route. If you have management traffic from more than one bridge group network, you need to specify a regular static route that identifies the network from which you expect management traffic.

  • In transparent mode, PPPoE is not supported for the Diagnostic interface.

  • Bidirectional Forwarding Detection (BFD) echo packets are not allowed through the FTD when using bridge group members. If there are two neighbors on either side of the FTD running BFD, then the FTD will drop BFD echo packets because they have the same source and destination IP address and appear to be part of a LAND attack.

Additional Guidelines and Requirements

  • The FTD does not support more than one 802.1Q header in a packet (known as Q-in-Q support) for firewall interfaces. Note that for all models except for the Firepower 4100/9300, inline sets and passive interfaces support Q-in-Q, up to two VLAN tags; the Firepower 4100/9300 models do not support Q-in-Q for any type of interface.

Configure Routed Mode Interfaces

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

This procedure describes how to set the name, security zone, and IPv4 address.

Before you begin

Procedure

Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

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

Step 3

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

Step 4

Enable the interface by checking the Enabled check box.

Step 5

(Optional) Set this interface to Management Only to limit traffic to management traffic; through-the-box traffic is not allowed.

Step 6

(Optional) Add a description in the Description field.

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

Step 7

In the Mode drop-down list, choose None.

Regular firewall interfaces have the mode set to None. The other modes are for IPS-only interface types.

Step 8

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

The routed interface is a Routed-type interface, and can only belong to Routed-type zones.

Step 9

See Configure the MTU for information about the MTU.

Step 10

Click the IPv4 tab. To set the IP address, use one of the following options from the IP Type drop-down list.

High Availability and clustering interfaces only support static IP address configuration; DHCP and PPPoE are not supported.

  • Use Static IP—Enter the IP address and subnet mask. For High Availabilty, you can only use a static IP address. Set the standby IP address on the Devices > Device Management > High Availability tab in the Monitored Interfaces area. If you do not set the standby IP address, the active unit cannot monitor the standby interface using network tests; it can only track the link state.

  • Use DHCP—Configure the following optional parameters:

    • Obtain default route using DHCP—Obtains the default route from the DHCP server.

    • DHCP route metric—Assigns an administrative distance to the learned route, between 1 and 255. The default administrative distance for the learned routes is 1.

  • Use PPPoE—If the interface is connected to a DSL, cable modem, or other connection to your ISP, and your ISP uses PPPoE to provide your IP address, configure the following parameters:

    • VPDN Group Name—Specify a group name of your choice to represent this connection.

    • PPPoE User Name—Specify the username provided by your ISP.

    • PPPoE Password/Confirm Password—Specify and confirm the password provided by your ISP.

    • PPP Authentication—Choose PAP, CHAP, or MSCHAP.

      PAP passes a cleartext username and password during authentication and is not secure. With CHAP, the client returns the encrypted [challenge plus password], with a cleartext username in response to the server challenge. CHAP is more secure than PAP, but it does not encrypt data. MSCHAP is similar to CHAP but is more secure because the server stores and compares only encrypted passwords rather than cleartext passwords as in CHAP. MSCHAP also generates a key for data encryption by MPPE.

    • PPPoE route metric—Assign an administrative distance to the learned route. Valid values are from 1 to 255. By default, the administrative distance for the learned routes is 1.

    • Store Username and Password in Flash—Stores the username and password in flash memory.

      The FTD device stores the username and password in a special location of NVRAM.

Step 11

(Optional) See Configure IPv6 Addressing to configure IPv6 addressing on the IPv6 tab.

Step 12

(Optional) See Configure the MAC Address to manually configure the MAC address on the Advanced tab.

Step 13

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

  • Duplex—Choose Full, Half, or Auto. Auto is the default when the interface supports it.

  • Speed—Choose 10, 100, 1000, or Auto. Auto is the default. The type of interface limits the options you can select.

Step 14

Click OK.

Step 15

Click Save.

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

Configure Transparent Mode Bridge Group Interfaces

A bridge group is a group of interfaces that the Firepower Threat Defense device bridges instead of routes. Bridge groups are only supported in Transparent Firewall Mode. For more information about bridge groups, see About Bridge Groups.

To configure bridge groups and associated interfaces, perform these steps.

Configure General Bridge Group Member Interface Parameters

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

This procedure describes how to set the name and security zone for each bridge group member interface. The same bridge group can include different types of interfaces: physical interfaces, VLAN subinterfaces, EtherChannels, and redundant interfaces. The Diagnostic interface is not supported.

Before you begin
Procedure
Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

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

Step 3

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

Step 4

Enable the interface by checking the Enabled check box.

Step 5

(Optional) Set this interface to Management Only to limit traffic to management traffic; through-the-box traffic is not allowed.

Step 6

(Optional) Add a description in the Description field.

The description can be up to 200 characters on a single line, without carriage returns.
Step 7

In the Mode drop-down list, choose None.

Regular firewall interfaces have the mode set to None. The other modes are for IPS-only interface types. After you assign this interface to a bridge group, the mode will show as Switched.

Step 8

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

The bridge group member interface is a Switched-type interface, and can only belong to Switched-type zones. Do not configure any IP address settings for this interface. You will set the IP address for the Bridge Virtual Interface (BVI) only. Note that the BVI does not belong to a zone, and you cannot apply access control policies to the BVI.

Step 9

See Configure the MTU for information about the MTU.

Step 10

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

  • Duplex—Choose Full, Half, or Auto. Auto is the default when the interface supports it.

  • Speed—Choose 10, 100, 1000, or Auto. Auto is the default. The type of interface limits the options you can select.

Step 11

(Optional) See Configure IPv6 Addressing to configure IPv6 addressing on the IPv6 tab.

Step 12

(Optional) See Configure the MAC Address to manually configure the MAC address on the Advanced tab.

Step 13

Click OK.

Step 14

Click Save.

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

Configure the Bridge Virtual Interface (BVI)

Each bridge group requires a BVI for which you configure an IP address. The FTD uses this IP address as the source address for packets originating from the bridge group. The BVI IP address must be on the same subnet as the connected network. For IPv4 traffic, the BVI IP address is required to pass any traffic. For IPv6 traffic, you must, at a minimum, configure the link-local addresses to pass traffic, but a global management address is recommended for full functionality, including remote management and other management operations.


Note

For a separate Diagnostic interface, a non-configurable bridge group (ID 301) is automatically added to your configuration. This bridge group is not included in the bridge group limit.

Before you begin

You cannot add the BVI to a security zone; therefore, you cannot apply Access Control policies to the BVI. You must apply your policy to the bridge group member interfaces based on their zones.

Procedure
Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

Choose Add Interfaces > Bridge Group Interface.

Step 3

In the Bridge Group ID field, enter the bridge group ID between 1 and 250.

Step 4

In the Description field, enter a description for this bridge group.

Step 5

On the Interfaces tab, click an interface and then click Add to move it to the Selected Interfaces area. Repeat for all interfaces that you want to make members of the bridge group.

Step 6

Click the IPv4 tab. In the IP Address field, enter the IPv4 address and subnet mask.

Do not assign a host address (/32 or 255.255.255.255) to the BVI. Also, do not use other subnets that contain fewer than 3 host addresses (one each for the upstream router, downstream router, and transparent firewall) such as a /30 subnet (255.255.255.252). The FTD device drops all ARP packets to or from the first and last addresses in a subnet. For example, if you use a /30 subnet and assign a reserved address from that subnet to the upstream router, then the FTD device drops the ARP request from the downstream router to the upstream router.

For High Availabilty, set the standby IP address on the Devices > Device Management > High Availability tab in the Monitored Interfaces area. If you do not set the standby IP address, the active unit cannot monitor the standby interface using network tests; it can only track the link state.

Step 7

(Optional) See Configure IPv6 Addressing to configure IPv6 addressing.

Step 8

(Optional) See Add a Static ARP Entry and Add a Static MAC Address and Disable MAC Learning for a Transparent Mode Bridge Group (for transparent mode only) to configure the ARP and MAC settings.

Step 9

Click OK.

Step 10

Click Save.

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

Configure a Diagnostic (Management) Interface for Transparent Mode

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

In transparent firewall mode, all interfaces must belong to a bridge group. The only exception is the Diagnostic slot/port interface. For the Firepower 4100/9300 chassis, the diagnostic interface ID depends on the mgmt-type interface that you assigned to the FTD logical device. You cannot use any other interface types as diagnostic interfaces. You can configure one diagnostic interface.

Before you begin

Do not assign this interface to a bridge group; a non-configurable bridge group (ID 301) is automatically added to your configuration. This bridge group is not included in the bridge group limit.

Procedure
Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

Click the edit icon () for the Diagnostic interface.

Step 3

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

Step 4

Click the IPv4 tab. To set the IP address, use one of the following options from the IP Type drop-down list.

  • Use Static IP—Enter the IP address and subnet mask.
  • Use DHCP—Configure the following optional parameters:

    • Obtain default route using DHCP—Obtains the default route from the DHCP server.

    • DHCP route metric—Assigns an administrative distance to the learned route, between 1 and 255. The default administrative distance for the learned routes is 1.

  • Use PPPoE—Configure the following parameters:

    • VPDN Group Name—Specify a group name.

    • PPPoE User Name—Specify the username provided by your ISP.

    • PPPoE Password/Confirm Password—Specify and confirm the password provided by your ISP.

    • PPP Authentication—Choose PAP, CHAP, or MSCHAP.

      PAP passes a cleartext username and password during authentication and is not secure. With CHAP, the client returns the encrypted [challenge plus password], with a cleartext username in response to the server challenge. CHAP is more secure than PAP, but it does not encrypt data. MSCHAP is similar to CHAP but is more secure because the server stores and compares only encrypted passwords rather than cleartext passwords as in CHAP. MSCHAP also generates a key for data encryption by MPPE.

    • PPPoE route metric—Assign an administrative distance to the learned route. Valid values are from 1 to 255. By default, the administrative distance for the learned routes is 1.

    • Enable Route Settings—To manually configure the PPPoE IP address, check this box and then enter the IP Address.

    • Store Username and Password in Flash—Stores the username and password in flash memory.

      The FTD device stores the username and password in a special location of NVRAM.

Step 5

(Optional) See Configure IPv6 Addressing to configure IPv6 addressing.

Step 6

(Optional) On the Advanced tab, configure optional settings.

Step 7

Click OK.

Step 8

Click Save.

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

Configure IPv6 Addressing

This section describes how to configure IPv6 addressing in routed and transparent mode.

About IPv6

This section includes information about IPv6.

IPv6 Addressing

You can configure two types of unicast addresses for IPv6:

  • Global—The global address is a public address that you can use on the public network. For a bridge group, this address needs to be configured for the BVI, and not per member interface. You can also configure a global IPv6 address for the management interface in transparent mode.

  • Link-local—The link-local address is a private address that you can only use on the directly-connected network. Routers do not forward packets using link-local addresses; they are only for communication on a particular physical network segment. They can be used for address configuration or for the Neighbor Discovery functions such as address resolution. In a bridge group, only member interfaces have link-local addresses; the BVI does not have a link-local address.

At a minimum, you need to configure a link-local address for IPv6 to operate. If you configure a global address, a link-local address is automatically configured on the interface, so you do not also need to specifically configure a link-local address. For bridge group member interfaces, when you configure the global address on the BVI, the Firepower Threat Defense device automatically generates link-local addresses for member interfaces. If you do not configure a global address, then you need to configure the link-local address, either automatically or manually.

Modified EUI-64 Interface IDs

RFC 3513: Internet Protocol Version 6 (IPv6) Addressing Architecture requires that the interface identifier portion of all unicast IPv6 addresses, except those that start with binary value 000, be 64 bits long and be constructed in Modified EUI-64 format. The Firepower Threat Defense device can enforce this requirement for hosts attached to the local link.

When this feature is enabled on an interface, the source addresses of IPv6 packets received on that interface are verified against the source MAC addresses to ensure that the interface identifiers use the Modified EUI-64 format. If the IPv6 packets do not use the Modified EUI-64 format for the interface identifier, the packets are dropped and the following system log message is generated: 


325003: EUI-64 source address check failed.

The address format verification is only performed when a flow is created. Packets from an existing flow are not checked. Additionally, the address verification can only be performed for hosts on the local link.

Configure a Global IPv6 Address

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

To configure a global IPv6 address for any routed mode interface and for the transparent mode BVI, perform the following steps.


Note

Configuring the global address automatically configures the link-local address, so you do not need to configure it separately.

For subinterfaces defined on the FTD, we recommend that you also set the MAC address manually, because they use the same burned-in MAC address of the parent interface. IPv6 link-local addresses are generated based on the MAC address, so assigning unique MAC addresses to subinterfaces allows for unique IPv6 link-local addresses, which can avoid traffic disruption in certain instances on the FTD. See Configure the MAC Address.

Procedure
Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

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

Step 3

Click the IPv6 tab.

For routed mode, the Basic tab is selected by default. For transparent mode, the Address tab is selected by default.

Step 4

Configure the global IPv6 address using one of the following methods.

  • (Routed interface) Stateless autoconfiguration—Check the Autoconfiguration check box.

    Enabling stateless autconfiguration on the interface configures IPv6 addresses based upon prefixes received in Router Advertisement messages. A link-local address, based on the Modified EUI-64 interface ID, is automatically generated for the interface when stateless autoconfiguration is enabled.

    Although RFC 4862 specifies that hosts configured for stateless autoconfiguration do not send Router Advertisement messages, the FTD device does send Router Advertisement messages in this case. Uncheck the IPv6 > Settings > Enable RA check box to suppress messages.

  • Manual configuration—To manually configure a global IPv6 address:

    1. Click the Address tab, and click Add Address.

      The Add Address dialog box appears.

    2. In the Address field, enter either a full global IPv6 address, including the interface ID, or enter the IPv6 prefix, along with the IPv6 prefix length. (Routed Mode) If you only enter the prefix, then be sure to check the Enforce EUI 64 check box to generate the interface ID using the Modified EUI-64 format. For example, 2001:0DB8::BA98:0:3210/48 (full address) or 2001:0DB8::/48 (prefix, with EUI 64 checked).

      For High Availabilty (if you did not set Enforce EUI 64), set the standby IP address on the Devices > Device Management > High Availability tab in the Monitored Interfaces area. If you do not set the standby IP address, the active unit cannot monitor the standby interface using network tests; it can only track the link state.

Step 5

For Routed interfaces, you can optionally set the following values on the Basic tab:

  • To automatically configure the link-local address when you do not configure the global address, check the Enable IPv6 check box.

    If you do not want to configure a global address, and only need to configure a link-local address, you have the option of generating the link-local addresses based on the interface MAC addresses (Modified EUI-64 format. Because MAC addresses use 48 bits, additional bits must be inserted to fill the 64 bits required for the interface ID.)

  • To enforce the use of Modified EUI-64 format interface identifiers in IPv6 addresses on a local link, check the Enforce EUI-64 check box.

  • To manually set the link-local address, enter an address in the Link-Local address field.

    A link-local address should start with FE8, FE9, FEA, or FEB, for example fe80::20d:88ff:feee:6a82. If you do not want to configure a global address, and only need to configure a link-local address, you have the option of manually defining the link-local address. Note that we recommend automatically assigning the link-local address based on the Modified EUI-64 format. For example, if other devices enforce the use of the Modified EUI-64 format, then a manually-assigned link-local address may cause packets to be dropped.

  • Check the Enable DHCP for address config check box to set the Managed Address Config flag in the IPv6 router advertisement packet.

    This flag in IPv6 router advertisements informs IPv6 autoconfiguration clients that they should use DHCPv6 to obtain addresses, in addition to the derived stateless autoconfiguration address.

  • Check the Enable DHCP for non-address config check box to set the Other Address Config flag in the IPv6 router advertisement packet.

    This flag in IPv6 router advertisements informs IPv6 autoconfiguration clients that they should use DHCPv6 to obtain additional information from DHCPv6, such as the DNS server address.

Step 6

For Routed interfaces, see Configure IPv6 Neighbor Discovery to configure settings on the Prefixes and Settings tabs. For BVI interfaces, see the following parameters on the Settings tab:

  • DAD attempts—The maximum number of DAD attempts, between 1 and 600. Set the value to 0 to disable duplicate address detection (DAD) processing. This setting configures the number of consecutive neighbor solicitation messages that are sent on an interface while DAD is performed on IPv6 addresses. 1 attempt is the default.

  • NS Interval—The interval between IPv6 neighbor solicitation retransmissions on an interface, between 1000 and 3600000 ms. The default value is 1000 ms.

  • Reachable Time—The amount of time that a remote IPv6 node is considered reachable after a reachability confirmation event has occurred, between 0 and 3600000 ms. The default value is 0 ms. When 0 is used for the value, the reachable time is sent as undetermined. It is up to the receiving devices to set and track the reachable time value. The neighbor reachable time enables detecting unavailable neighbors. Shorter configured times enable detecting unavailable neighbors more quickly, however, shorter times consume more IPv6 network bandwidth and processing resources in all IPv6 network devices. Very short configured times are not recommended in normal IPv6 operation.

Step 7

Click OK.

Step 8

Click Save.

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

Configure IPv6 Neighbor Discovery

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

The IPv6 neighbor discovery process uses ICMPv6 messages and solicited-node multicast addresses to determine the link-layer address of a neighbor on the same network (local link), verify the readability of a neighbor, and keep track of neighboring routers.

Nodes (hosts) use neighbor discovery to determine the link-layer addresses for neighbors known to reside on attached links and to quickly purge cached values that become invalid. Hosts also use neighbor discovery to find neighboring routers that are willing to forward packets on their behalf. In addition, nodes use the protocol to actively keep track of which neighbors are reachable and which are not, and to detect changed link-layer addresses. When a router or the path to a router fails, a host actively searches for functioning alternates.

Before you begin

Supported in Routed mode only.

Procedure
Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

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

Step 3

Click IPv6, and then Prefixes.

Step 4

(Optional) To configure which IPv6 prefixes are included in IPv6 router advertisements, perform the following steps:

  1. Click Add Prefix.

  2. In the Address field, enter the IPv6 address with the prefix length or check the Default check box to use the default prefix.

  3. (Optional) Uncheck the Advertisement check box to indicate that the IPv6 prefix is not advertised.

  4. Check the Off Link check box to indicate that the specified prefix is assigned to the link. Nodes sending traffic to addresses that contain the specified prefix consider the destination to be locally reachable on the link. This prefix should not be used for on-link determination.

  5. To use the specified prefix for autoconfiguration, check the Autoconfiguration check box.

  6. For the Prefix Lifetime, click Duration or Expiration Date.

    • Duration—Enter a Preferred Lifetime for the prefix in seconds. This setting is the amount of time that the specified IPv6 prefix is advertised as being valid. The maximum value represents infinity. Valid values are from 0 to 4294967295. The default is 2592000 (30 days). Enter a Valid Lifetime for the prefix in seconds. This setting is the amount of time that the specified IPv6 prefix is advertised as being preferred. The maximum value represents infinity. Valid values are from 0 to 4294967295. The default setting is 604800 (seven days). Alternatively, check the Infinite checkbox to set an unlimited duration.

    • Expiration Date—Choose a Valid and Preferred date and time.

  7. Click OK.

Step 5

Click Settings.

Step 6

(Optional) Set the maximum number of DAD attempts, between 1 and 600. 1 attempt is the default. Set the value to 0 to disable duplicate address detection (DAD) processing.

This setting configures the number of consecutive neighbor solicitation messages that are sent on an interface while DAD is performed on IPv6 addresses.

During the stateless autoconfiguration process, Duplicate Address Detection verifies the uniqueness of new unicast IPv6 addresses before the addresses are assigned to interfaces.

When a duplicate address is identified, the state of the address is set to DUPLICATE, the address is not used, and the following error message is generated: 


325002: Duplicate address ipv6_address/MAC_address on interface

If the duplicate address is the link-local address of the interface, the processing of IPv6 packets is disabled on the interface. If the duplicate address is a global address, the address is not used.

Step 7

(Optional) Configure the interval between IPv6 neighbor solicitation retransmissions in the NS Interval field, between 1000 and 3600000 ms.

The default value is 1000 ms.

Neighbor solicitation messages (ICMPv6 Type 135) are sent on the local link by nodes attempting to discover the link-layer addresses of other nodes on the local link. After receiving a neighbor solicitation message, the destination node replies by sending a neighbor advertisement message (ICPMv6 Type 136) on the local link.

After the source node receives the neighbor advertisement, the source node and destination node can communicate. Neighbor solicitation messages are also used to verify the reachability of a neighbor after the link-layer address of a neighbor is identified. When a node wants to verifying the reachability of a neighbor, the destination address in a neighbor solicitation message is the unicast address of the neighbor.

Neighbor advertisement messages are also sent when there is a change in the link-layer address of a node on a local link.

Step 8

(Optional) Configure the amount of time that a remote IPv6 node is considered reachable after a reachability confirmation event has occurred in the Reachable Time field, between 0 and 3600000 ms.

The default value is 0 ms. When 0 is used for the value, the reachable time is sent as undetermined. It is up to the receiving devices to set and track the reachable time value.

The neighbor reachable time enables detecting unavailable neighbors. Shorter configured times enable detecting unavailable neighbors more quickly, however, shorter times consume more IPv6 network bandwidth and processing resources in all IPv6 network devices. Very short configured times are not recommended in normal IPv6 operation.

Step 9

(Optional) To suppress the router advertisement transmissions, uncheck the Enable RA check box. If you enable router advertisement transmissions, you can set the RA lifetime and interval.

Router advertisement messages (ICMPv6 Type 134) are automatically sent in response to router solicitation messages (ICMPv6 Type 133). Router solicitation messages are sent by hosts at system startup so that the host can immediately autoconfigure without needing to wait for the next scheduled router advertisement message.

You may want to disable these messages on any interface for which you do not want the Firepower Threat Defense device to supply the IPv6 prefix (for example, the outside interface).

  • RA Lifetime—Configure the router lifetime value in IPv6 router advertisements, between 0 and 9000 seconds.

    The default is 1800 seconds.

  • RA Interval—Configure the interval between IPv6 router advertisement transmissions, between 3 and 1800 seconds.

    The default is 200 seconds.

Step 10

Click OK.

Step 11

Click Save.

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

Configure Advanced Interface Settings

This section describes how to configure MAC addresses for regular firewall mode interfaces, how to set the maximum transmission unit (MTU), and how to set other advanced parameters.

About Advanced Interface Configuration

This section describes advanced interface settings.

About MAC Addresses

You can manually assign MAC addresses to override the default.


Note

You might want to assign unique MAC addresses to subinterfaces defined on the FTD, because they use the same burned-in MAC address of the parent interface. For example, your service provider might perform access control based on the MAC address. Also, because IPv6 link-local addresses are generated based on the MAC address, assigning unique MAC addresses to subinterfaces allows for unique IPv6 link-local addresses, which can avoid traffic disruption in certain instances on the FTD.

Default MAC Addresses

Default MAC address assignments depend on the type of interface.

  • Physical interfaces—The physical interface uses the burned-in MAC address.

  • Redundant interfaces—A redundant interface uses the MAC address of the first physical interface that you add. If you change the order of the member interfaces in the configuration, then the MAC address changes to match the MAC address of the interface that is now listed first. If you assign a MAC address to the redundant interface, then it is used regardless of the member interface MAC addresses.

  • EtherChannels (Firepower Models)—For an EtherChannel, all interfaces that are part of the channel group share the same MAC address. This feature makes the EtherChannel transparent to network applications and users, because they only see the one logical connection; they have no knowledge of the individual links. The port-channel interface uses a unique MAC address from a pool; interface membership does not affect the MAC address.

  • EtherChannels (ASA Models)—The port-channel interface uses the lowest-numbered channel group interface MAC address as the port-channel MAC address. Alternatively you can configure a MAC address for the port-channel interface. We recommend configuring a unique MAC address in case the group channel interface membership changes. If you remove the interface that was providing the port-channel MAC address, then the port-channel MAC address changes to the next lowest numbered interface, thus causing traffic disruption.

  • Subinterfaces—All subinterfaces of a physical interface use the same burned-in MAC address. You might want to assign unique MAC addresses to subinterfaces. For example, your service provider might perform access control based on the MAC address. Also, because IPv6 link-local addresses are generated based on the MAC address, assigning unique MAC addresses to subinterfaces allows for unique IPv6 link-local addresses, which can avoid traffic disruption in certain instances on the FTD.

About the MTU

The MTU specifies the maximum frame payload size that the Firepower Threat Defense device can transmit on a given Ethernet interface. The MTU value is the frame size without Ethernet headers, VLAN tagging, or other overhead. For example, when you set the MTU to 1500, the expected frame size is 1518 bytes including the headers, or 1522 when using VLAN. Do not set the MTU value higher to accommodate these headers.

Path MTU Discovery

The Firepower Threat Defense device supports Path MTU Discovery (as defined in RFC 1191), which lets all devices in a network path between two hosts coordinate the MTU so they can standardize on the lowest MTU in the path.

Default MTU

The default MTU on the Firepower Threat Defense device is 1500 bytes. This value does not include the 18-22 bytes for the Ethernet header, VLAN tagging, or other overhead.

MTU and Fragmentation

For IPv4, if an outgoing IP packet is larger than the specified MTU, it is fragmented into 2 or more frames. Fragments are reassembled at the destination (and sometimes at intermediate hops), and fragmentation can cause performance degradation. For IPv6, packets are typically not allowed to be fragmented at all. Therefore, your IP packets should fit within the MTU size to avoid fragmentation.

For UDP or ICMP, the application should take the MTU into account to avoid fragmentation.


Note

The Firepower Threat Defense device can receive frames larger than the configured MTU as long as there is room in memory.

MTU and Jumbo Frames

A larger MTU lets you send larger packets. Larger packets might be more efficient for your network. See the following guidelines:

  • Matching MTUs on the traffic path—We recommend that you set the MTU on all FTD interfaces and other device interfaces along the traffic path to be the same. Matching MTUs prevents intermediate devices from fragmenting the packets.

  • Accommodating jumbo frames—You can set the MTU up to 9198 bytes. The maximum is 9000 for the Firepower Threat Defense Virtual and 9184 for the Firepower 4100/9300.

ARP Inspection for Bridge Group Traffic

By default, all ARP packets are allowed between bridge group members. You can control the flow of ARP packets by enabling ARP inspection.

ARP inspection prevents malicious users from impersonating other hosts or routers (known as ARP spoofing). ARP spoofing can enable a “man-in-the-middle” attack. For example, a host sends an ARP request to the gateway router; the gateway router responds with the gateway router MAC address. The attacker, however, sends another ARP response to the host with the attacker MAC address instead of the router MAC address. The attacker can now intercept all the host traffic before forwarding it on to the router.

ARP inspection ensures that an attacker cannot send an ARP response with the attacker MAC address, so long as the correct MAC address and the associated IP address are in the static ARP table.

When you enable ARP inspection, the Firepower Threat Defense device compares the MAC address, IP address, and source interface in all ARP packets to static entries in the ARP table, and takes the following actions:

  • If the IP address, MAC address, and source interface match an ARP entry, the packet is passed through.

  • If there is a mismatch between the MAC address, the IP address, or the interface, then the Firepower Threat Defense device drops the packet.

  • If the ARP packet does not match any entries in the static ARP table, then you can set the Firepower Threat Defense device to either forward the packet out all interfaces (flood), or to drop the packet.


    Note

    The dedicated Diagnostic interface never floods packets even if this parameter is set to flood.

MAC Address Table

When you use bridge groups, the FTD learns and builds a MAC address table in a similar way as a normal bridge or switch: when a device sends a packet through the bridge group, the FTD adds the MAC address to its table. The table associates the MAC address with the source interface so that the FTD knows to send any packets addressed to the device out the correct interface. Because traffic between bridge group members is subject to the FTD security policy, if the destination MAC address of a packet is not in the table, the FTD does not flood the original packet on all interfaces as a normal bridge does. Instead, it generates the following packets for directly-connected devices or for remote devices:

  • Packets for directly-connected devices—The FTD generates an ARP request for the destination IP address, so that it can learn which interface receives the ARP response.

  • Packets for remote devices—The FTD generates a ping to the destination IP address so that it can learn which interface receives the ping reply.

The original packet is dropped.

Default Settings

  • If you enable ARP inspection, the default setting is to flood non-matching packets.

  • The default timeout value for dynamic MAC address table entries is 5 minutes.

  • By default, each interface automatically learns the MAC addresses of entering traffic, and the Firepower Threat Defense device adds corresponding entries to the MAC address table.

Guidelines for ARP Inspection and the MAC Address Table

  • ARP inspection is only supported for bridge groups.

  • MAC address table configuration is only supported for bridge groups.

  • Bridge groups are only supported in transparent firewall mode.

Configure the MTU

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

Customize the MTU on the interface, for example, to allow jumbo frames.


Caution

Changing the highest MTU value on the device for a non-management/diagnostic interface restarts the Snort process when you deploy configuration changes, temporarily interrupting traffic inspection. Inspection is interrupted on all non-management/diagnostic interfaces, not just the interface you modified. Whether this interruption drops traffic or passes it without further inspection depends on the model of the managed device and the interface type. See Snort® Restart Traffic Behavior for more information.

Before you begin

  • Changing the MTU above 1500 bytes automatically enables jumbo frames; for ASA models, you must reload the system before you can use jumbo frames.

  • If you use an interface in an inline set, the MTU setting is not used. However, the jumbo frame setting is relevant to inline sets; jumbo frames enable the inline interfaces to receive packets up to 9000 bytes. To enable jumbo frames, you must set the MTU of any interface above 1500 bytes.

Procedure

Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

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

Step 3

On the General tab, set the MTU between 64 and 9198 bytes; the maximum is 9000 for the Firepower Threat Defense Virtual and 9184 for the FTD on the Firepower 4100/9300 chassis.

The default is 1500 bytes.

Step 4

Click OK.

Step 5

Click Save.

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

Step 6

For ASA models, if you set the MTU above 1500 bytes, reload the system to enable jumbo frames.

Configure the MAC Address

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

You might need to manually assign a MAC address. You can also set the Active and Standby MAC addresses on the Devices > Device Management > High Availability tab. If you set the MAC address for an interface on both screens, the addresses on the Interfaces > Advanced tab take precedence.

Procedure

Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

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

Step 3

Click the Advanced tab.

The Information tab is selected.
Step 4

In the Active MAC Address field, enter a MAC address in H.H.H format, where H is a 16-bit hexadecimal digit.

For example, the MAC address 00-0C-F1-42-4C-DE would be entered as 000C.F142.4CDE. The MAC address must not have the multicast bit set, that is, the second hexadecimal digit from the left cannot be an odd number.

Step 5

In the Standby MAC Address field, enter a MAC address for use with High Availability.

If the active unit fails over and the standby unit becomes active, the new active unit starts using the active MAC addresses to minimize network disruption, while the old active unit uses the standby address.

Step 6

Click OK.

Step 7

Click Save.

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

Add a Static ARP Entry

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

By default, all ARP packets are allowed between bridge group members. You can control the flow of ARP packets by enabling ARP inspection (see Configure ARP Inspection). ARP inspection compares ARP packets with static ARP entries in the ARP table.

For routed interfaces, you can enter static ARP entries, but normally dynamic entries are sufficient. For routed interfaces, the ARP table is used to deliver packets to directly-connected hosts. Although senders identify a packet destination by an IP address, the actual delivery of the packet on Ethernet relies on the Ethernet MAC address. When a router or host wants to deliver a packet on a directly connected network, it sends an ARP request asking for the MAC address associated with the IP address, and then delivers the packet to the MAC address according to the ARP response. The host or router keeps an ARP table so it does not have to send ARP requests for every packet it needs to deliver. The ARP table is dynamically updated whenever ARP responses are sent on the network, and if an entry is not used for a period of time, it times out. If an entry is incorrect (for example, the MAC address changes for a given IP address), the entry needs to time out before it can be updated with the new information.

For transparent mode, the FTD only uses dynamic ARP entries in the ARP table for traffic to and from the FTD device, such as management traffic.

Before you begin

This screen is only available for named interfaces.

Procedure

Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

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

Step 3

Click the Advanced tab, and then click the ARP tab (called ARP and MAC for transparent mode).

Step 4

Click Add ARP Config.

The Add ARP Config dialog box appears.
Step 5

In the IP Address field, enter the IP address of the host.

Step 6

In the MAC Address field, enter the MAC address of the host; for example, 00e0.1e4e.3d8b.

Step 7

To perform proxy ARP for this address, check the Enable Alias check box.

If the FTD device receives an ARP request for the specified IP address, then it responds with the specified MAC address.

Step 8

Click OK, and then click OK again to exit the Advanced settings.

Step 9

Click Save.

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

Add a Static MAC Address and Disable MAC Learning for a Transparent Mode Bridge Group

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

Normally, MAC addresses are added to the MAC address table dynamically as traffic from a particular MAC address enters an interface. You can disable MAC address learning; however, unless you statically add MAC addresses to the table, no traffic can pass through the FTD device. You can also add static MAC addresses to the MAC address table. One benefit to adding static entries is to guard against MAC spoofing. If a client with the same MAC address as a static entry attempts to send traffic to an interface that does not match the static entry, then the FTD device drops the traffic and generates a system message. When you add a static ARP entry (see Add a Static ARP Entry), a static MAC address entry is automatically added to the MAC address table.

Before you begin

This screen is only available for named interfaces.

Procedure

Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

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

Step 3

Click the Advanced tab, and then click the ARP and MAC tab.

Step 4

(Optional) Disable MAC learning by unchecking the Enable MAC Learning check box.

Step 5

To add a static MAC address, click Add MAC Config.

The Add MAC Config dialog box appears.
Step 6

In the MAC Address field, enter the MAC address of the host; for example, 00e0.1e4e.3d8b. Click OK.

Step 7

Click OK to exit the Advanced settings.

Step 8

Click Save.

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

Set Security Configuration Parameters

Smart License Classic License Supported Devices Supported Domains Access

Any

N/A

FTD

Any

Admin
Access Admin
Network Admin

This section describes how to prevent IP spoofing, allow full fragment reassembly, and override the default fragment setting set for at the device level in Platform Settings .

Anti-Spoofing

This section lets you enable Unicast Reverse Path Forwarding on an interface. Unicast RPF guards against IP spoofing (a packet uses an incorrect source IP address to obscure its true source) by ensuring that all packets have a source IP address that matches the correct source interface according to the routing table.

Normally, the FTD device only looks at the destination address when determining where to forward the packet. Unicast RPF instructs the device to also look at the source address; this is why it is called Reverse Path Forwarding. For any traffic that you want to allow through the FTD device, the device routing table must include a route back to the source address. See RFC 2267 for more information.

For outside traffic, for example, the FTD device can use the default route to satisfy the Unicast RPF protection. If traffic enters from an outside interface, and the source address is not known to the routing table, the device uses the default route to correctly identify the outside interface as the source interface.

If traffic enters the outside interface from an address that is known to the routing table, but is associated with the inside interface, then the FTD device drops the packet. Similarly, if traffic enters the inside interface from an unknown source address, the device drops the packet because the matching route (the default route) indicates the outside interface.

Unicast RPF is implemented as follows:

  • ICMP packets have no session, so each packet is checked.

  • UDP and TCP have sessions, so the initial packet requires a reverse route lookup. Subsequent packets arriving during the session are checked using an existing state maintained as part of the session. Non-initial packets are checked to ensure they arrived on the same interface used by the initial packet.

Fragment per Packet

By default, the FTD device allows up to 24 fragments per IP packet, and up to 200 fragments awaiting reassembly. You might need to let fragments on your network if you have an application that routinely fragments packets, such as NFS over UDP. However, if you do not have an application that fragments traffic, we recommend that you do not allow fragments through the FTD device. Fragmented packets are often used as DoS attacks.

Fragment Reassembly

The FTD device performs the following fragment reassembly processes:

  • IP fragments are collected until a fragment set is formed or until a timeout interval has elapsed.

  • If a fragment set is formed, integrity checks are performed on the set. These checks include no overlapping, no tail overflow, and no chain overflow.

  • IP fragments that terminate at the FTD device are always fully reassembled.

  • If Full Fragment Reassembly is disabled (the default), the fragment set is forwarded to the transport layer for further processing.

  • If Full Fragment Reassembly is enabled, the fragment set is first coalesced into a single IP packet. The single IP packet is then forwarded to the transport layer for further processing.

Before you begin

This screen is only available for named interfaces.

Procedure

Step 1

Select Devices > Device Management and click the edit icon () for your FTD device. The Interfaces tab is selected by default.

Step 2

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

Step 3

Click the Advanced tab, and then click the Security Configuration tab.

Step 4

To enable Unicast Reverse Path Forwarding, check the Anti-Spoofing check box.

Step 5

To enable full fragment reassembly, check the Full Fragment Reassembly check box.

Step 6

To change the number of fragments allowed per packet, check the Override Default Fragment Setting check box, and set the following values:

  • Size—Set the maximum number of packets that can be in the IP reassembly database waiting for reassembly. The default is 200. Set this value to 1 to disable fragments.

  • Chain—Set the maximum number of packets into which a full IP packet can be fragmented. The default is 24 packets.

  • Timeout—Set the maximum number of seconds to wait for an entire fragmented packet to arrive. The timer starts after the first fragment of a packet arrives. If all fragments of the packet do not arrive by the number of seconds specified, all fragments of the packet that were already received will be discarded. The default is 5 seconds.

Step 7

Click OK.

Step 8

Click Save.

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

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