> GRE Tunnel Interface Configuration Mode Commands
> The Generic Routing Encapsulation (GRE) Tunnel Interface Configuration Mode is used to create and manage the GRE tunneling interfaces for addresses, address resolution options, etc.
> Important: The commands or keywords/variables that are available are dependent on platform type, product version, and installed license(s).
> destination
> This command configures the destination IPv4 address of the tunnel by specifying the IPv4 destination end address. This is a mandatory configuration for GRE tunnel interface.
> Product
> All
> Privilege
> Security Administrator, Administrator
> Syntax
> [no] destination address ip_address
> no
> Removes/disassociates the configured destination IP address from specific GRE tunnel interface configuration.
> address ip_address
> Configures the IP address for the interface specifying the IPv4 IP address.
> ip_address must be specified using the standard IPv4 dotted decimal notation.
> Usage
> Use this command to configure the destination IPv4 address of the tunnel by specifying the IP address of destination tunnel end for GRE tunnel interface.
> Important: State of source address will affect the operational state of the tunnel.
> Example
> The following command sets the 1.2.3.4 as destination IP address of the GRE tunnel interface:
> destination address 1.2.3.4
> end
> Exits the interface configuration mode and returns to the Exec mode.
> Product
> All
> Privilege
> Security Administrator, Administrator
> Syntax
> end
> Usage
> Change the mode back to the Exec mode.
> exit
> Exits the Interface Configuration Mode and returns to the Context Configuration Mode.
> Product
> All
> Privilege
> Security Administrator, Administrator
> Syntax
> exit
> Usage
> Return to the context configuration mode.
> keepalive
> This command configures various parameters for sending Keepalives to the remote end-point in GRE tunnel interface configuration. By default sending keepalives is disabled.
> Product
> All
> Privilege
> Security Administrator, Administrator
> Syntax
> keepalive [interval time_interval num-retry retry]
> [default | no] keepalive
> default
> Sets the sending of Keepalives with default parameters.
> interval: 10 seconds
> num-retry: 3 retries
> no
> Disables the keepalive and turns off the sending of Keepalives messages.
> interval time_interval
> Default: 10
> Specifies the time interval (in seconds) between two Keepalives sent to remote ends of GRE tunnel interface configuration.
> time_interval must be an integer from 5 through 3600.
> num-retry retry
> Default: 3
> Specifies number of retransmission of keepalives to remote node without getting any response before the remote node is marked as dead/down.
> retry must be an integer between 0 through 10.
> Usage
> Use this command to configure the parameters for sending Keepalives to the remote end-point of GRE tunnel. It also configures the interval at which GRE Keepalives are sent on the interface and number of retries without getting a response from the remote end-point before the tunnel is shutdown. By default, Keepalives will not be sent.
> Example
> The following command enables the keepalive and sets the other parameters to defaults:
> default keepalive
> source
> This command configures the source IPv4 address of the tunnel either by specifying the IP address (host address) or by specifying another configured non-tunnel IPv4 interface. This is a mandatory configuration for GRE tunnel interface.
> Product
> All
> Privilege
> Security Administrator, Administrator
> Syntax
> [no] source {address ip_address | interface interface_name}
> no
> Removes/disassociates the configured source IP address or host interface from specific GRE tunnel interface configuration.
> address ip_address
> Configures the IP address for the interface specifying the IPv4 IP address.
> ip_address must be specified using the standard IPv4 dotted decimal notation.
> interface interface_name
> Specifies the name of the preconfigured non-tunnel IPv4 interface, whose address is used as the source address of the GRE tunnel.
> Usage
> Use this command to configure the source IPv4 address of the tunnel either by specifying the IP address (host address) or by specifying another configured non-tunnel IPv4 interface for GRE tunnel interface.
> Important: State of source address will affect the operational state of the tunnel.
> Example
> The following command sets the 1.2.3.4 as source IP address of the GRE tunnel interface:
> source address 1.2.3.4
> tos
> This command configures the parameters/action for the TOS parameter in the IPv4 tunnel transport protocol header.
> Product
> All
> Privilege
> Security Administrator, Administrator
> Syntax
> ip tos {value [ af11 | af12 | af13 | af21 | af22 | af23 | af31 | af32 | af33 | af41 | af42 | af43 | be | ef | lower-bits tos_value] | copy}
> no ip tos
> default
> Sets the IP TOS to lower bits value of 0.
> value [tos_value]
> Default: af11
> Specifies the IP QoS DSCP per-hop behavior to be marked on the outer header of signalling packets originating from the Access Gateway. This is a standards-based feature (RFC 2597). The following forwarding types are supported:
> af11: Designates the use of Assured Forwarding 11 per-hop behavior
> af12: Designates the use of Assured Forwarding 12 per-hop behavior
> af13: Designates the use of Assured Forwarding 13 per-hop behavior
> af21: Designates the use of Assured Forwarding 21 per-hop behavior
> af22: Designates the use of Assured Forwarding 22 per-hop behavior
> af23: Designates the use of Assured Forwarding 23 per-hop behavior
> af31: Designates the use of Assured Forwarding 31 per-hop behavior
> af32: Designates the use of Assured Forwarding 32 per-hop behavior
> af33: Designates the use of Assured Forwarding 33 per-hop behavior
> af41: Designates the use of Assured Forwarding 41 per-hop behavior
> af42: Designates the use of Assured Forwarding 42 per-hop behavior
> af43: Designates the use of Assured Forwarding 43 per-hop behavior
> be: Designates the use of Best Effort forwarding per-hop behavior
> ef: Designates the use of Expedited Forwarding per-hop behavior typically dedicated to low-loss, low-latency traffic.
> The assured forwarding behavior groups are listed in the table below.

> | Class 1 | Class 2 | Class 3 | Class 4
> Low Drop | AF11 | AF21 | AF31 | AF41
> Medium Drop | AF12 | AF22 | AF32 | AF42
> High Drop | AF13 | AF23 | AF33 | AF43

> ‌
> Traffic marked with a higher class is given priority during congestion periods. If congestion occurs to traffic with the same class, the packets with the higher AF value are dropped first.
> lower-bits tos_value
> Default: 0
> Sets the least-significant 6 bits in the TOS byte with the specified numeric value.
> tos_value must be an integer from 0 through 255.
> copy
> This keyword instructs the system to copy the TOS value from the passenger IPv4 packet or Traffic class value from the passenger IPv6 packet to the TOS value of the IPv4 tunnel transport protocol header
> Usage
> Use this command either to set the TOS parameter in the IPv4 tunnel transport protocol header to the specified value or instructs to copy the TOS value from the passenger IPv4 packet or Traffic class value from the passenger IPv6 packet to the TOS value of the IPv4 tunnel transport protocol header. If one of the enumerated values is set, the DSCP bits which are the six most-significant bits in the TOS byte are marked. If the integer value is set, it will be written into the six least-significant bits of the TOS byte.
> Example
> The following command instructs the system to copy the TOS value from the passenger IPv4 packet or Traffic class value from the passenger IPv6 packet to the TOS value of the IPv4 tunnel transport protocol header:
> tos copy
> ttl
> This command configures the Time to live (TTL) parameter to be used in the tunnel transport protocol header for the current GRE tunnel interface.
> Product
> All
> Privilege
> Security Administrator, Administrator
> Syntax
> ttl ttl_value
> default ttl
> default
> Sets the TTL value to system default value; i.e. 15.
> ttl_value
> Default: 15
> Specifies the maximum time to live to be used in the tunnel transport protocol header
> The time to live (TTL) is not a measure of time but the number of hops through the network.
> ttl_value must be an integer between 1 through 255.
> Usage
> Use this command to set the TTL parameter to be used in tunnel transport protocol header for GRE tunnel configuration.
> Example
> The following configures the IP address to associate with the interface:
> ttl 10

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