Navigation Path

Devices > VPN > Site To Site. Then Add VPN > Firepower Threat Defense Device, or edit a listed VPN Topology. Open the Endpoint tab.

Fields

Device

Choose an endpoint node for your deployment:

• A FTD device managed by this FMC

• A FTD high availability container managed by this FMC

• An Extranet device, any device (Cisco or third party) not managed by this FMC.

Device Name

For extranet devices only, provide a name for this device. We recommend naming it such that it is identifiable as an unmanaged device.

Interface

If you chose a managed device as your endpoint, choose an interface on that managed device.

For 'Point to Point' deployments, you can also configure an endpoint with dynamic interface. An endpoint with a dynamic interface can pair only with an extranet device and can’t pair with an endpoint, which has a managed device.

You can configure device interfaces at Devices > Device Management > Add/Edit device > Interfaces.

IP Address

• If you choose an extranet device, a device not managed by the FMC, specify an IP address for the endpoint.

  For an extranet device, select Static and specify an IP address or select Dynamic to allow dynamic extranet devices.

  If you have chosen point-to-point topology and either IKEv1 or IKEv2, you can configure backup peers by entering the primary and backup peer IP addresses separated by a comma.

• If you chose a managed device as an endpoint, choose a single IPv4 address or multiple IPv6 addresses from the drop-down list. These IP addresses are already assigned to this interface on the managed device.

• All endpoints in a topology must have the same IP addressing scheme. IPv4 tunnels can carry IPv6 traffic and vice versa. The Protected Networks define which addressing scheme the tunneled traffic uses.

• If the managed device is a high-availability container, choose from a list of interfaces.

This IP is Private

Check the check box if the endpoint resides behind a firewall with network address translation (NAT).

Note	Use this option only when the peer is managed by the same FMC and don’t use this option if the peer is an extranet device.

Public IP address

If you checked the This IP is Private check box, specify a public IP address for the firewall. If the endpoint is a responder, specify this value.

Connection Type

Specify the allowed negotiation as bidirectional, answer-only, or originate-only. Supported combinations for the connection type are:

Table 1. Connection Type Supported Combinations

Remote Node	Central Node
Originate-Only	Answer-Only
Bi-Directional	Answer-Only
Bi-Directional	Bi-Directional

Certificate Map

Choose a preconfigured certificate map object, or click Add () to add a certificate map object. The certificate map defines what information is necessary in the received client certificate to be valid for VPN connectivity. See Certificate Map Objects for details.

Protected Networks

Caution

Hub and Spoke topology—To avoid traffic drop for a dynamic crypto map, ensure that you don’t select the protected network any for both the endpoints. If the protected network is configured as any, on both the endpoints, the crypto ACL that works upon the tunnel is not generated.

Defines the networks that are protected by this VPN endpoint. Select the networks by selecting the list of Subnet/IP Address that define the networks that are protected by this endpoint. Click Add () to select from available Network Objects or add new Network Objects. See Creating Network Objects. Access control lists are generated from the choices made here.

• Subnet/IP Address (Network)—VPN endpoints can’t have the same IP address and protected networks in a VPN endpoint pair cannot overlap. If protected networks for an endpoint contain IPv4 or IPv6 entries, the other endpoint's protected network must have at least one entry of the same type (IPv4 or IPv6). If it doesn’t, the other endpoint's IP address must be of the same type and not overlap with the entries in the protected network. (Use /32 CIDR address blocks for IPv4 and /128 CIDR address blocks for IPv6.) If both of these checks fail, the endpoint pair is invalid.

  Note

  By default, Reverse Route Injection is enabled is enabled in Firepower Management Center. Subnet/IP Address (Network) remains the default selection. When you’ve selected Protected Networks as Any and observe default route traffic being dropped, disable the Reverse Route Injection. Choose VPN> Site to Site > edit a VPN > IPsec > Enable Reverse Route Injection. Deploy the configuration changes to remove set reverse-route (Reverse Route Injection) from the crypto map configuration and remove the VPN-advertised reverse route that causes the reverse tunnel traffic to be dropped.

• Access List (Extended)—An extended access list provides the capability to control the type of traffic that will be accepted by this endpoint, like GRE or OSPF traffic. Traffic may be restricted either by address or port. Click Add () to add access control list objects.

  Note	Access Control List is supported only in the point to point topology.

Advanced Settings

Enable Dynamic Reverse Route Injection—Reverse Route Injection (RRI) enables routes to be automatically inserted into the routing process, for the networks and hosts protected by a remote tunnel endpoint. Dynamic RRI routes are created only upon the successful establishment of IPsec security associations (SA’s).

Note

Dynamic RRI is supported only on IKEv2, and not supported on IKEv1 or IKEv1 + IKEv2. Dynamic RRI isn’t supported on originate-only peer, Full Mesh topology, and Extranet peer. In Point-to-Point, only one peer can have dynamic RRI enabled. Between Hub and Spoke, only one of the endpoints can have dynamic RRI enabled. Dynamic RRI cannot be combined with a dynamic crypto map.

Send Local Identity to Peers—Select this option to send local identity information to the peer device. Select one of the following Local Identity Configuration from the list and configure the local identity:

• IP address—Use the IP address of the interface for the identity.

• Auto—Use the IP address for pre-shared key and Cert DN for certificate-based connections.

• Email ID—Specify the email ID to use for the identity. The email ID can be up to 127 characters.

• Hostname—Use the fully qualified hostname.

• Key ID—Specify the key-id to use for the identity. The key ID must be fewer than 65 characters.

The local identity is used to configure a unique identity per IKEv2 tunnel, instead of a global identity for all the tunnels. The unique identity allows FTD to have multiple IPsec tunnels behind a NAT to connect to the Cisco Umbrella Secure Internet Gateway (SIG).

For information about configuring a unique tunnel ID on Umbrella, see Cisco Umbrella SIG User Guide.

VPN Filter—Select an extended access list from the list or click Add to create a new extended access list object to filter the site-to-site VPN traffic.

The VPN filter provides more security and filters site-to-site VPN data using an extended access list. The extended access list object selected for the VPN filter lets you filter pre-encrypted traffic before entering the VPN tunnel and decrypted traffic that exits a VPN tunnel. The sysopt permit-vpn option, when enabled, would bypass the access control policy rules for the traffic coming from the VPN tunnel. When the sysopt permit-vpn option is enabled, the VPN filter helps in identifying and filtering the site-to-site VPN traffic.

Note	The VPN filter is supported only on Point to Point, and Hub and Spoke topologies. It isn’t supported on Mesh topology.

For Hub and Spoke topology, you can choose to override the hub VPN filter on the spoke endpoints in case a different VPN filter needs to enabled on a specific tunnel.

Select the Override VPN Filter on the Hub option to override the hub VPN filter on the spokes. Select the Remote VPN Filter extended access list object or create an access list to override.

Note	For an extranet device as a spoke, only the Override VPN filter on the Hub option is available.

For more information about sysopt permit-VPN, see FTD Advanced Site-to-site VPN Tunnel Options.

For the versions of IKE you have chosen for this topology, specify the IKEv1/IKEv2 Settings.

Note	Settings in this dialog apply to the entire topology, all tunnels, and all managed devices.

Navigation Path

Devices > VPN > Site To Site. Then Add VPN > Firepower Threat Defense Device, or edit a listed VPN Topology. Open the IKE tab.

Fields

Policy

Choose the required IKEv1 or IKEv2 policy objects from the predefined list or create new objects to use. You can choose multiple IKEv1 and IKEv2 policies. IKEv1 and IKEv2 support a maximum of 20 IKE policies, each with a different set of values. Assign a unique priority to each policy that you create. The lower the priority number, the higher the priority.

For details, see FTD IKE Policies

Authentication Type

Site-to-site VPN supports two authentication methods, pre-shared key and certificate. For an explanation of the two methods, see Deciding Which Authentication Method to Use.

Note	In a VPN topology that supports IKEv1, the Authentication Method specified in the chosen IKEv1 Policy object becomes the default in the IKEv1 Authentication Type setting. These values must match, otherwise, your configuration will error.

• Pre-shared Automatic Key—The FMC automatically defines the pre-shared key for this VPN. Specify the Pre-shared Key Length, the number of characters in the key, 1-27.

  The character " (double quote) isn’t supported as part of pre-shared keys. If you’ve used " in a pre-shared key, ensure that you change the character after you upgrade to Firepower Threat Defense 6.30 or higher.

• Pre-shared Manual Key—Manually assign the pre-shared key for this VPN. Specify the Key and then reenter the same to Confirm Key.

  When you choose this option for IKEv2, the Enforce hex-based pre-shared key only check box appears, check if desired. If enforced, you must enter a valid hex value for the key, an even number of 2-256 characters, using numerals 0-9, or A-F.

• Certificate—When you use certificates as the authentication method for VPN connections, peers obtain digital certificates from a CA server in your PKI infrastructure, and trade them to authenticate each other.

  In the Certificate field, select a preconfigured certificate enrollment object. This enrollment object generates a trustpoint with the same name on the managed device. The certificate enrollment object should be associated with and installed on the device, post which the enrollment process is complete, and then a trustpoint is created.

  A trustpoint is a representation of a CA or identity pair. A trustpoint includes the identity of the CA, CA-specific configuration parameters, and an association with one enrolled identity certificate.

  Before you select this option, note the following:

  • Ensure you’ve enrolled a certificate enrollment object on all the endpoints in the topology—A certificate enrollment object contains the Certification Authority (CA) server information and enrollment parameters that are required for creating Certificate Signing Requests (CSRs) and obtaining Identity Certificates from the specified CA. Certificate Enrollment Objects are used to enroll your managed devices into your PKI infrastructure, and create trustpoints (CA objects) on devices that support VPN connections. For instructions on creating a certificate enrollment object, see Adding Certificate Enrollment Objects, and for instructions on enrolling the object on the endpoints see one of the following as applicable:

    • Installing a Certificate Using Self-Signed Enrollment

    • Installing a Certificate using EST Enrollment

    • Installing a Certificate Using SCEP Enrollment

    • Installing a Certificate Using Manual Enrollment

    • Installing a Certificate Using a PKCS12 File

    Note	For a site-to-site VPN topology, ensure that the same certificate enrollment object is enrolled in all the endpoints in the topology. For further details, see the table below.

  • Refer the following table to understand the enrollment requirement for different scenarios. Some of the scenarios require you to override the certificate enrollment object for specific devices. See Managing Object Overrides to understand how to override objects.

    Certificate Enrollment Types	Device identity certificate for all endpoints is from the same CA		Device identity certificate for all endpoints is from different CAs
    	Device-specific parameters are NOT specified in the certificate enrollment object	Device-specific parameters are specified in the certificate enrollment object
    Manual	No override required	Override required	Override required
    EST	No override required	Override required	Override required
    SCEP	No override required	Override required	Override required
    PKCS	Override required	Override required	Override required
    Self-signed	Not applicable	Not applicable	Not applicable

  • Understand the VPN certificate limitations mentioned in Firepower Threat Defense VPN Certificate Guidelines and Limitations.

  Note

  If you use a Windows Certificate Authority (CA), the default application policies extension is IP security IKE intermediate. If you use this default setting, you must select the Ignore IPsec Key Usage option in the Advanced Settings section on the Key tab in the PKI Certificate Enrollment dialog box for the object you select. Otherwise, the endpoints can’t complete the site-to-site VPN connection.

Note	Settings in this dialog apply to the entire topology, all tunnels, and all managed devices.

Crypto-Map Type

A crypto map combines all the components required to set up IPsec security associations (SA). When two peers try to establish an SA, they must each have at least one compatible crypto map entry. The IPsec security negotiation uses the proposals defined in the crypto map entry to protect the data flows specified by that crypto map’s IPsec rules. Choose static or dynamic for this deployment's crypto-map:

• Static—Use a static crypto map in a point-to-point or full mesh VPN topology.

• Dynamic—Dynamic crypto-maps essentially create a crypto map entry without all the parameters configured. The missing parameters are later dynamically configured (as the result of an IPsec negotiation) to match a remote peer’s requirements.

  Dynamic crypto map policies are applicable to both hub-and-spoke and point-to-point VPN topologies. To apply these policies, specify a dynamic IP address for one of the peers in the topology and ensure that the dynamic crypto-map is enabled on this topology. In a full mesh VPN topology, you can apply only static crypto map policies.

IKEv2 Mode

For IPsec IKEv2 only, specify the encapsulation mode for applying ESP encryption and authentication to the tunnel. This determines what part of the original IP packet has ESP applied.

• Tunnel mode—(default) Encapsulation mode is set to tunnel mode. Tunnel mode applies ESP encryption and authentication to the entire original IP packet (IP header and data), hiding the ultimate source and destination addresses and becoming the payload in a new IP packet.

  The major advantage of tunnel mode is that you don’t need to modify the end systems to receive the benefits of IPsec. This mode allows a network device, such as a router, to act as an IPsec proxy. That is, the router performs encryption on behalf of the hosts. The source router encrypts packets and forwards them along the IPsec tunnel. The destination router decrypts the original IP datagram and forwards it onto the destination system. Tunnel mode also protects against traffic analysis; with tunnel mode, an attacker can only determine the tunnel endpoints and not the true source and destination of the tunneled packets, even if they are the same as the tunnel endpoints.

• Transport preferred—Encapsulation mode is set to transport mode with an option to fall back to tunnel mode if the peer doesn’t support it. In transport mode only the IP payload is encrypted, and the original IP headers are left intact. Therefore, the admin must select a protected network that matches the VPN interface IP address.

  This mode has the advantages of adding only a few bytes to each packet and allowing devices on the public network to see the final source and destination of the packet. With transport mode, you can enable special processing (for example, QoS) on the intermediate network based on the information in the IP header. However, the layer 4 header is encrypted, which limits examination of the packet.

• Transport required— Encapsulation mode is set to transport mode only, falling back to tunnel mode is allowed. If the endpoints can’t successfully negotiate transport mode, due to one endpoint not supporting it, the VPN connection is not made.

Proposals

Click Edit () to specify the proposals for your chosen IKEv1 or IKEv2 method. Select from the available IKEv1 IPsec Proposals or IKEv2 IPsec Proposals objects, or create and then select a new one. See Configure IKEv1 IPsec Proposal Objects and Configure IKEv2 IPsec Proposal Objects for details.

Enable Security Association (SA) Strength Enforcement

Enabling this option ensures that the encryption algorithm used by the child IPsec SA isn’t stronger (in terms of the number of bits in the key) than the parent IKE SA.

Enable Reverse Route Injection

Reverse Route Injection (RRI) enables static routes to be automatically inserted into the routing process for those networks and hosts protected by a remote tunnel endpoint.

Enable Perfect Forward Secrecy

Whether to use Perfect Forward Secrecy (PFS) to generate and use a unique session key for each encrypted exchange. The unique session key protects the exchange from subsequent decryption, even if the entire exchange was recorded and the attacker has obtained the preshared or private keys used by the endpoint devices. If you select this option, also select the Diffie-Hellman key derivation algorithm to use when generating the PFS session key in the Modulus Group list.

Modulus Group

The Diffie-Hellman group to use for deriving a shared secret between the two IPsec peers without transmitting it to each other. A larger modulus provides higher security but requires more processing time. The two peers must have a matching modulus group. For a full explanation of the options, see Deciding Which Diffie-Hellman Modulus Group to Use.

Lifetime Duration

The number of seconds a security association exists before expiring. The default is 28,800 seconds.

Lifetime Size

The volume of traffic (in kilobytes) that can pass between IPsec peers using a given security association before it expires. The default is 4,608,000 kilobytes. Infinite data isn’t allowed.

ESPv3 Settings

Validate incoming ICMP error messages

Choose whether to validate ICMP error messages received through an IPsec tunnel and destined for an interior host on the private network.

Enable 'Do Not Fragment' Policy

Define how the IPsec subsystem handles large packets that have the do-not-fragment (DF) bit set in the IP header.

Policy

• Copy DF bit—Maintains the DF bit.

• Clear DF bit—Ignores the DF bit.

• Set DF bit—Sets and uses the DF bit.

Enable Traffic Flow Confidentiality (TFC) Packets

Enable dummy TFC packets that mask the traffic profile which traverses the tunnel. Use the Burst, Payload Size, and Timeout parameters to generate random length packets at random intervals across the specified SA.

Note

You can enable dummy Traffic Flow Confidentiality (TFC) packets at random lengths and intervals on an IPsec security association (SA). You must have an IKEv2 IPsec proposal set before enabling TFC. Enabling TFC packets prevents the VPN tunnel from being idle. Thus the VPN idle timeout configured in the group policy doesn’t work as expected when you enable the TFC packets.

The following sections describe the advanced options you can specify in your site-to-site VPN deployment. These settings apply to the entire topology, all tunnels, and all managed devices.