aws_route Error: more than 1 targe specified if you change the destination type

[peteromoon]

If you change the destination type of an aws_route, for example from a network interface (network_interface_id) to an internet gateway (gateway_id), when you run terraform apply it fails with:

* aws_route.test: 1 error(s) occurred:

* aws_route.test: Error: more than 1 target specified. Only 1 of gateway_id, egress_only_gateway_id, nat_gateway_id, instance_id, network_interface_id, route_table_id or vpc_peering_connection_id is allowed.

This type of change could occur if you change a subnet from being "private" to "public" or change from using an instance as a NAT gateway to using an AWS NAT gateway.

Terraform Version

$ terraform -v
Terraform v0.9.2

Affected Resource(s)

Please list the resources as a list, for example:

• aws_route

Terraform Configuration Files

Step 1, Terraform config

{
  "provider" : {
    "aws" : {
      "region" : "eu-west-1"
    },
  },
  "resource" : {
    "aws_route_table" : {
      "test" : {
        "vpc_id" : "${aws_vpc.test.id}",
        "propagating_vgws" : [ ],
      }
    },
    "aws_route" : {
      "test" : {
        "destination_cidr_block" : "0.0.0.0/0",
        "network_interface_id" : "${aws_network_interface.test.id}",
        "route_table_id" : "${aws_route_table.test.id}"
      }
    },
    "aws_route_table_association" : {
      "test" : {
        "subnet_id" : "${aws_subnet.test.id}",
        "route_table_id" : "${aws_route_table.test.id}"
      }
    },
    "aws_internet_gateway" : {
      "test" : {
        "vpc_id" : "${aws_vpc.test.id}",
      }
    },
    "aws_vpc" : {
      "test" : {
        "cidr_block" : "10.247.0.0/17",
        "instance_tenancy" : "default",
        "enable_dns_support" : true,
        "enable_dns_hostnames" : true,
      }
    },
    "aws_subnet" : {
      "test" : {
        "vpc_id" : "${aws_vpc.test.id}",
        "availability_zone" : "eu-west-1a",
        "cidr_block" : "10.247.0.0/23",
      }
    },
    "aws_network_interface" : {
      "test" : {
        "source_dest_check" : false,
        "subnet_id": "${aws_subnet.test.id}"
      }
    }
  }
}

Step 2, Terraform config

{
  "provider" : {
    "aws" : {
      "region" : "eu-west-1"
    },
  },
  "resource" : {
    "aws_route_table" : {
      "test" : {
        "vpc_id" : "${aws_vpc.test.id}",
        "propagating_vgws" : [ ],
      }
    },
    "aws_route" : {
      "test" : {
        "destination_cidr_block" : "0.0.0.0/0",
        "gateway_id" : "${aws_internet_gateway.test.id}",
        "route_table_id" : "${aws_route_table.test.id}"
      }
    },
    "aws_route_table_association" : {
      "test" : {
        "subnet_id" : "${aws_subnet.test.id}",
        "route_table_id" : "${aws_route_table.test.id}"
      }
    },
    "aws_internet_gateway" : {
      "test" : {
        "vpc_id" : "${aws_vpc.test.id}",
      }
    },
    "aws_vpc" : {
      "test" : {
        "cidr_block" : "10.247.0.0/17",
        "instance_tenancy" : "default",
        "enable_dns_support" : true,
        "enable_dns_hostnames" : true,
      }
    },
    "aws_subnet" : {
      "test" : {
        "vpc_id" : "${aws_vpc.test.id}",
        "availability_zone" : "eu-west-1a",
        "cidr_block" : "10.247.0.0/23",
      }
    },
    "aws_network_interface" : {
      "test" : {
        "source_dest_check" : false,
        "subnet_id": "${aws_subnet.test.id}"
      }
    }
  }
}

Expected Behavior

The route to destination 0.0.0.0/0 is changed from a network interface to the internet gateway when the terraform config is changed and terraform apply is run.

Actual Behavior

terraform apply failed with an error when route is changed in terraform config from a network interface destination to an internet gateway destination.

Steps to Reproduce

To reproduce:

1. Using Step 1 terraform config (see above) run: terraform apply
2. Change route destination from network interface to internet gateway to produce Step 2 terraform config (see above)
3. Run terraform apply
4. Fails with error above.

References

I found this issue that is similar

• aws_route Error: more than 1 target specified. #6076

[UnclaimedPants]

@peteromoon I've run into this same issue too.

[aschepp]

We also run into this issue.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

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