Aviatrix GRE configuration. 
This connection has two GRE tunnels between the customer gateway and Aviatrix gateways in the cloud.
Tunnel #1 is the primary tunnel. The customer gateway should be configured in such a way that it should
switch over to tunnel #2 when tunnel #1 fails.
Tunnel #1 (Primary)
================================================================================
GRE (Generic Routing Encapsulation) inserts additional
headers to transmit packets. These headers require additional space, 
which reduces the amount of space available to transmit application data.
To limit the impact of this behavior, we recommend the following 
configuration on your Customer Gateway:
  - TCP MSS Adjustment       : 1387 bytes
  - Clear Don't Fragment Bit : enabled
  - Fragmentation            : Before encapsulation
#3: Tunnel Interface Configuration
Your Customer Gateway must be configured with a tunnel interface that is
associated with the GRE tunnel. Please make sure that the tunnel interface responds
to ICMP echo request. Traffic that should go through the tunnel
should be specified by following your gateway's configuration guide, using the
information below.
Gateway IP addresses:
  - Customer Gateway                : 192.168.101.101
  - Aviatrix Gateway Public IP      : 13.57.79.250
  - Aviatrix Gateway Private IP     : 10.32.1.115,10.32.1.96,10.32.1.73,10.32.1.105,10.32.1.76,10.32.1.108,10.32.1.109,10.32.1.79,10.32.1.80,10.32.1.81,10.32.1.86,10.32.1.87,10.32.1.120,10.32.1.89,10.32.1.126
Subnets:
  - Customer Network(s)             : N/A for transit network
  - Cloud Networks(s)               : N/A for transit network
Tunnel Inside IP addresses:
  - Customer Gateway                : 169.254.39.189/30
  - Aviatrix Gateway                : 169.254.39.190/30
Configure your tunnel to fragment at the optimal size:
  - Tunnel interface MTU     : 1436 bytes
#4. Border Gateway Protocol (BGP) Configuration:
The Border Gateway Protocol (BGPv4) is used to exchange routes from the VPC to on-prem
network. Each BGP router has an Autonomous System Number (ASN).
BGP Configuration:
  - BGP Mode                        : true
  - Customer Gateway ASN            : 65080
  - Aviatrix Gateway ASN            : 65010
  - BGP MD5 Authentication Key      : 
Configure BGP to receive routes from on-prem network. Aviatrix Transit gateway will announce
prefixes to your on-prem  gateway based upon the spokes you have attached
Tunnel #2 (Backup)
================================================================================
GRE (Generic Routing Encapsulation) inserts additional
headers to transmit packets. These headers require additional space, 
which reduces the amount of space available to transmit application data.
To limit the impact of this behavior, we recommend the following 
configuration on your Customer Gateway:
  - TCP MSS Adjustment       : 1387 bytes
  - Clear Don't Fragment Bit : enabled
  - Fragmentation            : Before encapsulation
#3: Tunnel Interface Configuration
Your Customer Gateway must be configured with a tunnel interface that is
associated with the GRE tunnel. Traffic that should go through the tunnel
should be specified by following your gateway's configuration guide, using the
information below.
Gateway IP addresses:
  - Customer Gateway                : 192.168.101.101
  - Aviatrix Gateway Public IP      : 50.18.114.77
  - Aviatrix Gateway Private IP     : 10.32.1.212,10.32.1.224,10.32.1.225,10.32.1.226,10.32.1.228,10.32.1.197,10.32.1.199,10.32.1.231,10.32.1.240,10.32.1.209,10.32.1.210,10.32.1.213,10.32.1.247,10.32.1.215,10.32.1.250
Subnets:
  - Customer Network(s)             : N/A for transit network
  - Cloud Networks(s)               : N/A for transit network 
Tunnel Inside IP addresses:
  - Customer Gateway                : 169.254.205.217/30
  - Aviatrix Gateway                : 169.254.205.218/30
Configure your tunnel to fragment at the optimal size:
  - Tunnel interface MTU     : 1436 bytes
#4. Border Gateway Protocol (BGP) Configuration:
The Border Gateway Protocol (BGPv4) is used to exchange routes from the VPC to on-prem
network. Each BGP router has an Autonomous System Number (ASN).
BGP Configuration:
  - BGP Mode                        : true
  - Customer Gateway ASN            : 65080
  - Aviatrix Gateway ASN            : 65010
  - BGP MD5 Authentication Key      : 
Configure BGP to receive routes from on-prem network. Aviatrix Transit gateway will announce
prefixes to your on-prem  gateway based upon the spokes you have attached
For vendor specific instructions, please go to the following URL:
http://docs.aviatrix.com/#site2cloud