About FTD Interfaces
The FTD includes data interfaces as well as a management/diagnostic interface.
When you attach a cable to an interface connection, you need to configure the interface. At minimum, you need to name the interface and enable it for it to pass traffic. If the interface is a member of a bridge group, this is sufficient. For non-bridge group members, you also need to give the interface an IP address. If you intend to create VLAN subinterfaces rather than a single physical interface on a given port, you would typically configure the IP addresses on the subinterface, not on the physical interface. VLAN subinterfaces let you divide a physical interface into multiple logical interfaces that are tagged with different VLAN IDs, which is useful when you connect to a trunk port on a switch.
The interface list shows the available interfaces, their names, addresses, and states. You can change the state of an interface, on or off, directly in the list of interfaces. The list shows the interface characteristics based on your configuration. Use the open/close arrow on a bridge group interface to view the member interfaces, which also appear by themselves in the list.
The following topics explain the limitations of configuring interfaces through Firepower Device Manager as well as other interface management concepts.
You can configure one of the following modes for each interface:
Each Layer 3 routed interface requires an IP address on a unique subnet. You would typically attach these interfaces to switches, a port on another router, or to an ISP/WAN gateway.
A bridge group is a group of interfaces that the FTD bridges instead of routes. 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.
You can route between routed interfaces and BVIs, if you name the BVI. In this case, the BVI acts as the gateway between member interfaces and routed interfaces. If you do not name the BVI, traffic on the bridge group member interfaces cannot leave the bridge group. Normally, you would name the interface so that you can route member interfaces to the internet.
One use for a bridge group in routed mode is to use extra interfaces on the Firepower Threat Defense device instead of an external switch. You can attach endpoints directly to bridge group member interfaces. You can also attach switches to add more endpoints to the same network as the BVI.
The physical port labeled Management actually has two separate interfaces associated with it.
Management virtual interface—This IP address is used for system communication. This is the address the system uses for Smart Licensing and to retrieve database updates. You can open management sessions to it (Firepower Device Manager and CLI). You must configure a management address, which is defined on.
Diagnostic physical interface—The physical Management port is actually named Diagnostic. You can use this interface to send syslog messages to an external syslog server. Configuring an IP address for the Diagnostic physical interface is optional. The only reason to configure the interface is if you want to use it for syslog. This interface appears, and is configurable, on thepage. The Diagnostic physical interface only allows management traffic, and does not allow through traffic.
The recommended way to configure Management/Diagnostic is to not wire the physical port to a network. Instead, configure the Management IP address only, and configure it to use the data interfaces as the gateway for obtaining updates from the Internet. Then, open the inside interfaces to HTTPS/SSH traffic (by default, HTTPS is enabled) and open Firepower Device Manager using the inside IP address (see Configuring the Management Access List).
Recommendations for Configuring a Separate Management Network
If you want to use a separate management network, wire the physical Management/Diagnostic interface to a switch or router.
Then, configure the following:
Selectand configure IPv4 or IPv6 addresses (or both) on the attached network. If you want to, you can configure a DHCP server to provide IPv4 addresses to other endpoints on the network. If there is a router with a route to the internet on the management network, use that as the gateway. Otherwise, use the data interfaces as the gateway.
Configure an address for the Diagnostic interface (on) only if you intend to send syslog messages through the interface to a syslog server. Otherwise, do not configure an address for Diagnostic, it is not needed. Any IP address you configure must be on the same subnet as the management IP address and cannot be the in DHCP server pool. For example, the default configuration uses 192.168.45.45 as the management address, and 192.168.45.46-192.168.45.254 as the DHCP pool, so you can configure Diagnostic using any address from 192.168.45.1 to 192.168.45.44.
Limitations for Management/Diagnostic Interface Configuration for a Separate Management Network
If you wire the physical Management interface, ensure that you follow these limitations:
If you want a DHCP server on the management network, configure it on the Management interface (). You cannot configure a DHCP server on the Diagnostic (physical) interface.
If there is another DHCP server on the management network, disable it or the DHCP server running on Management. As a rule, a given subnet should have no more than one DHCP server.
If you configure addresses for both Management and Diagnostic, ensure that they are on the same subnet.
You can use the data interfaces as the management gateway even if you configure an IP address for Diagnostic. But Diagnostic will not use the data interfaces as a gateway. If you need a path from Diagnostic to other networks, another router on the management network needs to route the traffic originating from the Diagnostic IP address. If necessary, configure static routes for the Diagnostic interface (select).
Each interface can be assigned to a single security zone. You then apply your security policy based on zones. For example, you can assign the inside interface to the inside zone; and the outside interface to the outside zone. You can configure your access control policy to enable traffic to go from inside to outside, but not from outside to inside, for example.
For bridge groups, you add member interfaces to the zones, you cannot add the Bridge Virtual Interface (BVI).
You do not include the Diagnostic/Management interface in a zone. Zones apply to data interfaces only.
You can create security zones on the Objects page.
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, you configure the global address on the Bridge Virtual Interface (BVI), not on each member interface. You cannot specify any of the following as a global address.
Internally reserved IPv6 addresses: fd00::/56 (from=fd00:: to= fd00:0000:0000:00ff:ffff:ffff:ffff:ffff)
An unspecified address, such as ::/128
The loopback address, ::1/128
multicast addresses, ff00::/8
Link-local addresses, fe80::/10
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 Network Discovery functions such as address resolution and neighbor discovery. In a bridge group, enabling IPv6 on the BVI automatically configures link-local addresses for each bridge group member interface. Each interface must have its own address because the link-local address is only available on a segment, and is tied to the interface MAC 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. If you do not configure a global address, then you need to configure the link-local address, either automatically or manually.
For RJ-45 interfaces, the default auto-negotiation setting also includes the Auto-MDI/MDIX feature. Auto-MDI/MDIX eliminates the need for crossover cabling by performing an internal crossover when a straight cable is detected during the auto-negotiation phase. Either the speed or duplex must be set to auto-negotiate to enable Auto-MDI/MDIX for the interface. If you explicitly set both the speed and duplex to a fixed value, thus disabling auto-negotiation for both settings, then Auto-MDI/MDIX is also disabled. For Gigabit Ethernet, when the speed and duplex are set to 1000 and full, then the interface always auto-negotiates; therefore Auto-MDI/MDIX is always enabled and you cannot disable it.