Route Propagation

[pcrum]

Currently, a user has to manually enable route propagation on the subscriber VPC. Is it possible to have route propagation enabled by default when subscriber VPC is being instantiated or configured?

[jpeezus]

yes you would have to change the SubscriberVPC template to enable route propagation and it will be turned on during launch.

[freimer]

in commonLambdaFunctions.py:

def createVgwAttachToVpc(vpcId, vgwAsn, region, paGroup):
    """Creates a VGW and attach it to the VPC, returns VgwId
    """
    try:
        tags = [{'Key': 'Name', 'Value': paGroup}]
        import time
        ec2Connection = boto3.client('ec2', region_name=region)
        # Create VGW with vgwAsn
        response = ec2Connection.create_vpn_gateway(Type='ipsec.1', AmazonSideAsn=int(vgwAsn))
        vgw_id = response['VpnGateway']['VpnGatewayId']
        # Attach VGW to VPC
        while True:
            status = ec2Connection.attach_vpn_gateway(VpcId=vpcId, VpnGatewayId=vgw_id,
                                                      DryRun=False)['VpcAttachment']
            if status['State'] == 'attaching':
                time.sleep(2)
            elif status['State'] == 'attached':
                ec2Connection.create_tags(Resources=[vgw_id], Tags=tags)
                # Propagate routes to routing table
                route_tables = ec2Connection.describe_route_tables(
                    Filters=[{'Name': 'vpc-id', 'Values': [vpcId]},{'Name': 'association.main', 'Values': ['false']}])
                ec2Connection.enable_vgw_route_propagation(RouteTableId=route_tables['RouteTables'][0]['RouteTableId'],
                                                           GatewayId=vgw_id)
                return vgw_id
            else:
                return None
        # return response['VpnGateway']['VpnGatewayId']
    except Exception as e:
        logger.error("Error creating Vgw and Attaching it to VPC, Error : {}".format(str(e)))
        return False

This assumes that there are no additional route tables created in the subscribing VPC other than the non-default one created by the CF/TF template. The relevant change is the addition of these lines:

                # Propagate routes to routing table
                route_tables = ec2Connection.describe_route_tables(
                    Filters=[{'Name': 'vpc-id', 'Values': [vpcId]},{'Name': 'association.main', 'Values': ['false']}])
                ec2Connection.enable_vgw_route_propagation(RouteTableId=route_tables['RouteTables'][0]['RouteTableId'],
                                                           GatewayId=vgw_id)