terraform-aviatrix-mc-overlap-nat-spoke

Description

This configures Aviatrix spoke gateways to deal with IP overlap in the spoke VNET/VPC by adding NAT rules and route propagation. The actual spoke gateway deployment happens outside of this module. It can be combined with the Aviatrix spoke deployment modules.

This module uses hide-nat (Source-NAT, SNAT) to hide all traffic initiated from the spoke VNET/VPC behind a unique gateway IP address. In order to expose services hosted inside the VNET/VPC to the outside world, a combination of destination NAT (DNAT) and SNAT is used.

Make sure to include gw1_snat_addr, gw2_snat_addr and any dst_cidr's in the dnat rules in the spoke gateway included_advertised_spoke_routes attribute.

Diagram

Compatibility

Module version	Terraform version	Controller version	Terraform provider version
v1.1.1	1.1.0-1.2.2	>=7.0	>=0.3.0

Usage Example

module "spoke1_nat" {
  source  = "terraform-aviatrix-modules/mc-overlap-nat-spoke/aviatrix"
  version = "1.1.1"

  #Tip, use count on the module to create or destroy the NAT rules based on spoke gateway attachement
  #Example: count = var.attached ? 1 : 0 #Deploys the module only if var.attached is true.

  spoke_gw_object = data.aviatrix_spoke_gateway.spoke1
  spoke_cidrs = ["172.31.0.0/20",]
  transit_gw_name = "avx-transit-gw"
  gw1_snat_addr = "10.255.1.1"
  gw2_snat_addr = "10.255.1.2"
  dnat_rules = {
      rule1 = {
          dst_cidr = "10.255.255.1/32",
          dst_port = "80",
          protocol = "tcp",
          dnat_ips = "172.31.16.4",
          dnat_port = "80",
      },
      rule2 = {
          dst_cidr = "10.255.255.1/32",
          dst_port = "8443",
          protocol = "tcp",
          dnat_ips = "172.31.16.4",
          dnat_port = "443",
      },      
      rule3 = {
          dst_cidr = "10.255.255.2/32",
          dst_port = "80",
          protocol = "tcp",
          dnat_ips = "172.31.16.5",
          dnat_port = "80",
      },           
  }
}

Variables

The following variables are required:

key	value
spoke_gw_object	The Aviatrix spoke gateway object with all attributes
spoke_cidrs	VNET or VPC CIDRs (typically one, but can be multiple)
transit_gw_name	Name of the transit gateway, to determine the connection for SNAT rule.
gw1_snat_addr	IP Address to be used for hide natting traffic sourced from the spoke VNET/VPC

The following variables are optional:

key	default	value
gw2_snat_addr		IP Address to be used for hide natting traffic sourced from the spoke VNET/VPC. Required when spoke is HA pair.
dnat_rules		Contains the properties to create the DNAT rules. When left empty, only SNAT for traffic initiated from the spoke VNET/VPC is configured. Create as many unique rules as you like.
egress_nat	false	When enabled, SNAT rules for access towards the internet are enabled. E.g. for distributed FQDN egress.
uturnnat	false	Set to true to also make the DNAT IP reachable inside the spoke VNET/VPC through U-Turn NAT.

Outputs

This module will return the following outputs:

key	description
\	\

terraform-aviatrix-modules / terraform-aviatrix-mc-overlap-nat-spoke

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