# Enable GRE keepalive for a tunnel interface on an NGFW Engine

When you enable GRE keepalive for a tunnel interface on an NGFW Engine, GRE keepalive is used in all GRE route-based VPN tunnels where the tunnel interface is an endpoint.

##

Note: The router to which the NGFW Engine is connected must support GRE keepalive.

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

## Steps

1. Right-click an NGFW Engine, then select Edit <element type>.
2. Browse to Interfaces.
3. Right-click a tunnel interface, then select Properties.
4. On the Tunnel tab, enable GRE keepalive.
   1. Make sure that No Encryption is selected from the Encryption drop-down list.
   2. In the Tunnel options section, select Use GRE Keepalive.
   3. Configure the settings.
5. Click OK.
6. Click Save and Refresh.

## Tunnel Interface Properties dialog box (Firewall or Virtual Firewall)

Use this dialog box to configure properties of Tunnel Interface for Firewalls and Virtual Firewalls.

Option | Definition
--- | ---
General tab
Tunnel Interface ID | Select the ID for the Tunnel Interface. The Tunnel Interface ID is automatically mapped to the physical network interface on the engine according to the routing configuration.
Zone (Optional) | Select the network zone to which the interface belongs. Click Select to select an element, or click New to create an element.
Comment (Optional) | A comment for your own reference.

Option | Definition
--- | ---
QoS Mode (Optional) | Defines how QoS is applied to the link on this interface. If Full QoS or DSCP Handling and Throttling is selected, a QoS policy must also be selected. If Full QoS is selected, the throughput must also be defined. If the interface is a Physical Interface, the same QoS mode is automatically applied to any VLANs created under it.
QoS Policy | (When QoS Mode is Full QoS or DSCP Handling and Throttling) The QoS policy for the link on this interface. If the interface is a Physical Interface, the same QoS policy is automatically selected for any VLANs created under it. Note: If a Virtual Resource has a throughput limit defined, the interfaces on the Virtual NGFW Engine that use a QoS policy all use the same policy. The policy used in the first interface is used for all the interfaces.
Interface Throughput Limit | (When QoS Mode is Full QoS) Enter the throughput for the link on this interface as megabits per second. If the interface is a Physical Interface, the same throughput is automatically applied to any VLANs created under it. The throughput is for uplink speed (outgoing traffic) and typically must correspond to the speed of an Internet link (such as an ADSL line), or the combined speeds of several such links when connected to a single interface. CAUTION: Make sure that you set the interface speed correctly. When the bandwidth is set, the NGFW Engine always scales the total amount of traffic on this interface to the bandwidth you defined. This scaling happens even if there are no bandwidth limits or guarantees defined for any traffic. CAUTION: The throughput for a Physical Interface for a Virtual NGFW Engine must not be higher than the throughput for the Master NGFW Engine interface that hosts the Virtual NGFW Engine. Contact the administrator of the Master NGFW Engine before changing this setting.

Option | Definition
--- | ---
Tunnel tab
Tunnel | The selected Route-Based VPN Tunnel element. Click Select to select an element, or click New to create an element.
Tunnel Properties | The details of the selected Route-Based VPN Tunnel element.
Name (Optional) | The name of the tunnel.
Enabled | When selected, the tunnel is enabled.
Tunnel Type | Specifies the protocol used in the tunnel. GRE — Generic Routing Encapsulation. This tunnel type is compatible with gateways from most vendors. IP-IP — IP in IP. This tunnel type is for use with third-party gateways that only support IP-IP. SIT — Simple Internet Transition. This tunnel type is for use with IPv6 addresses. VPN — This tunnel type negotiates IPsec tunnels in the same way as policy-based VPNs, but traffic is sent into the tunnel based on routing. Note: For the VPN tunnel type, tunnels between all endpoints of both gateways are automatically created.
Encryption (Not when Tunnel Type is VPN) | The encryption mode for the tunnel. Transport Mode — The tunnel uses IPsec in transport mode. Tunnel Mode — The tunnel uses IPsec in tunnel mode. No Encryption — The tunnel is not encrypted. CAUTION: This option defines a tunnel in which traffic is not protected by a VPN. The No Encryption option is recommended only when you create tunnels entirely within protected networks or you are testing and troubleshooting routing and connectivity.
VPN Profile (Optional) (When Tunnel Type is VPN) (When Encryption is Transport Mode) | The VPN Profile element that defines the settings for authentication, integrity checking, and encryption for the tunnel. Note: Settings in the VPN Profile that do not apply to route-based VPN tunnels, such as IPsec Client settings, are ignored. Examples of available profiles: VPN-A Suite — The tunnel uses the VPN-A Suite VPN Profile element. The VPN-A Suite VPN Profile contains the VPN settings specified for the cryptographic suite “VPN-A” in RFC 4308. iOS Suite — The tunnel uses the iOS Suite VPN Profile element. The iOS Suite VPN Profile element contains only iOS-compatible encryption algorithms and protocols. Click Select to select an element. VPN-A Suite is selected by default.
Edit (When Tunnel Type is VPN) (When Encryption is Transport Mode) | Allows you to use pre-shared key authentication for the gateways involved in the tunnel. Note: The pre-shared key must be long and random to provide a secure VPN. Change the pre-shared key periodically (for example, monthly). Make sure that it is not possible for outsiders to obtain the key while you transfer it to other devices.
VPN (When Encryption is Tunnel Mode) | The policy-based VPN that provides the encryption for the tunnel. Click Select to select an element, or click New to create an element.
Tunnel Options section
PMTU Discovery (All tunnel types except VPN) | When selected, enables path MTU (PMTU) discovery. Select this option if you use dynamic routing and want to automatically determine the Maximum Transmission Unit (MTU) size on the network path to avoid IP fragmentation.
TTL (Optional) (All tunnel types except VPN) | Specifies the initial time-to-live (TTL) value that is inserted into the encapsulation header of packets that enter the tunnel. This setting is needed when dynamic routing is used. You can usually use the default value. The default TTL value is 64.
MTU (Optional) | Specifies the maximum transmission unit (MTU) value that defines the largest unit of data that can be transmitted without fragmenting a packet. Set the MTU size as large as possible, but not so large that it causes packets to be fragmented. You can usually use the default value.
Tunnel Group (When Tunnel Type is VPN) (When Encryption is Transport Mode) | Select the Tunnel Group to put the tunnel in. You can monitor the status of grouped tunnels in the Home view. By default, new tunnels are included in the Uncategorized group, which is a system Tunnel Group element.
Use GRE Keepalive (When Tunnel Type is GRE and Encryption is No Encryption) | When selected, the NGFW Engine sends keepalive packets at the specified interval to check that the GRE tunnel is still functioning. If the NGFW Engine does not receive a reply after the specified number of packets, the GRE tunnel is considered to be down. Period — The interval (in seconds) at which keepalive packets are sent. The default is 10 seconds. A value of 0 means that the NGFW Engine only replies to keepalive packets from other devices, but does not send keepalive packets itself. Retry — The number of packets after which the GRE tunnel is considered to be down if the NGFW Engine does not receive a reply. The default is 3 packets. Note: To use GRE keepalive, the router to which the NGFW Engine is connected must support GRE keepalive.

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