AWS clone VPC route table and routes.

README.md

AWS clone VPC route table and routes

Python script to clone an existing VPC route table. Script output is a series of AWS CLI calls to create the route table and assign routes.

Update AWS_TARGET_REGION and SOURCE_ROUTE_TABLE_ID to suit.

Note: does not currently support NAT Gateways routes due to Boto 2 API limitation.

Example

$ ./clone-route-table.py

# output generated...
routeTableID=$(aws ec2 create-route-table --region REGION --vpc-id vpc-XXXXXXXX --output text | grep "^ROUTETABLE" | cut -f2)
echo "Route table: $routeTableID"

aws ec2 create-route --region REGION --route-table-id $routeTableID --destination-cidr-block 172.60.20.10/32 --gateway-id igw-XXXXXXXX
aws ec2 create-route --region REGION --route-table-id $routeTableID --destination-cidr-block x.x.x.x/24 ----vpc-peering-connection-id pcx-XXXXXXXX
# and so on...

clone-route-table.py

#!/usr/bin/env python

import sys
import boto.vpc

AWS_TARGET_REGION = "ap-southeast-2"
SOURCE_ROUTE_TABLE_ID = "rtb-XXXXXXXX"
ROUTE_STATE_CREATED = "CreateRoute"


def exit_error(message):
    sys.stderr.write("Error: {0}\n".format(message))
    sys.exit(1)


def route_table_route_list(vpc_conn):
    # query VPC for source route table
    route_table_list = vpc_conn.get_all_route_tables([SOURCE_ROUTE_TABLE_ID])

    # note: for some reason route table is returned in a list of many routes - extract what we need
    route_table_item = None
    for route_table_check in route_table_list:
        if route_table_check.id is not None:
            # found it
            route_table_item = route_table_check
            break

    if route_table_item is None:
        # can't find requested route table
        exit_error("Unable to locate route table {0}".format(SOURCE_ROUTE_TABLE_ID))

    # return route table VPC ID and route list
    return route_table_item.vpc_id, route_table_item.routes


def generate_awscli_commands(vpc_id, route_list):
    # command to create a new route table
    print(
        'routeTableID=$(aws ec2 create-route-table --region {0} --vpc-id {1} --output text | grep "^ROUTETABLE" | cut -f2)\n'
        'echo "Route table: $routeTableID"\n'.format(AWS_TARGET_REGION, vpc_id)
    )

    # commands to create routes for route table
    for route_item in route_list:
        # ensure route has been explicitly created and has a CIDR block
        if (route_item.origin != ROUTE_STATE_CREATED) or (
            route_item.destination_cidr_block is None
        ):
            continue

        # get AWS CLI parameter type and value to re-create route
        route_type_param, route_value = awscli_route_type_param_value(route_item)
        if route_type_param is None:
            # unable to create route type - skip
            continue

        print(
            "aws ec2 create-route --region {0} --route-table-id $routeTableID --destination-cidr-block {1} --{2} {3}".format(
                AWS_TARGET_REGION,
                route_item.destination_cidr_block,
                route_type_param,
                route_value,
            )
        )


def awscli_route_type_param_value(route_item):
    # Internet/virtual gateway
    if route_item.gateway_id is not None:
        return "gateway-id", route_item.gateway_id

    # network interface
    if route_item.interface_id is not None:
        return "network-interface-id", route_item.interface_id

    # VPC peering connection
    if route_item.vpc_peering_connection_id is not None:
        return "vpc-peering-connection-id", route_item.vpc_peering_connection_id

    # note: NAT Gateway (not currently implemented by boto)
    # if (route_item.XXXX is not None):
    # 	return 'nat-gateway-id',route_item.XXXX

    # skip route item
    return None, None


def main():
    # make connection to VPC
    vpc_conn = boto.vpc.connect_to_region(AWS_TARGET_REGION)

    # fetch route list for route table
    route_table_vpc_id, route_list = route_table_route_list(vpc_conn)

    # generate AWS CLI commands
    generate_awscli_commands(route_table_vpc_id, route_list)


if __name__ == "__main__":
    main()