don't understand what is aws_route in vpc and it's purpose?

[Koby Meir]

I have configured my own aws vpc with terraform and i was unable to access my serves until i looked in the aws-2-tier examples and found this snippet:



# Grant the VPC internet access on its main route table
resource "aws_route" "internet_access" {
  route_table_id = "${aws_vpc.default.main_route_table_id}"
  destination_cidr_block = "0.0.0.0/0"
  gateway_id = "${aws_internet_gateway.default.id}"
}

Once i added it everything started to work again, but i'm still unsure to what it actually does and what does it change within AWS assets?

Thanks,

Koby

[Andrew Langhorn]

Hi Koby,

The aws_route resource adds a route to the route table to direct traffic destined for a particular CIDR block through a specific gateway. That gateway is then responsible for routing the traffic for that CIDR block onward.

In this case, you're adding a destination (0.0.0.0/0, which is shorthand for everything) to the route table defined by aws_vpc.default.main_route_table_id and defining the gateway defined by aws_internet_gateway.default.id as being responsible for routing packets destined toward that route through the internet gateway.

An internet gateway sits as a bridge between the outside world and a public subnet in a VPC, allowing internet access in to your VPC.

Does that make things a little clearer?

Andrew

[Koby Meir]

I understand the meaning of IGW and routing, i still don't understand why i need aws_route defined while i have aws_route_table and aws_route_table_association  defined for each one of my subet?

And what this piece of code actually does on AWS account, as i couldn't notice any change on my AWS VPC configuration with or without this code.

Thanks for the help.

Koby

[Andrew Hodgson]

Hi,

I had a similar issue when I first started using Terraform. The routes are the individual entries in the route table. Routes can also be defined inline with the route table, but I have found it is better to define them separately and assign them to the route table as if define inline you can end up with some dependency problems.

It's the same with security groups, you define the security group, then create each security group rule and assign it to the group. Those can also be defined inline.

Hope this helps,
Andrew.

________________________________________
From: terrafo...@googlegroups.com [terrafo...@googlegroups.com] on behalf of Koby Meir [koby...@gmail.com]
Sent: 28 July 2016 13:28
To: Terraform
Cc: andrew....@thoughtworks.com
Subject: Re: [terraform] don't understand what is aws_route in vpc and it's purpose?

I understand the meaning of IGW and routing, i still don't understand why i need aws_route defined while i have aws_route_table and aws_route_table_association defined for each one of my subet?
And what this piece of code actually does on AWS account, as i couldn't notice any change on my AWS VPC configuration with or without this code.

Thanks for the help.
Koby



On Thursday, July 28, 2016 at 1:52:47 AM UTC+3, Andrew Langhorn wrote:
Hi Koby,

The aws_route resource adds a route to the route table to direct traffic destined for a particular CIDR block through a specific gateway. That gateway is then responsible for routing the traffic for that CIDR block onward.

In this case, you're adding a destination (0.0.0.0/0<http://0.0.0.0/0>, which is shorthand for everything) to the route table defined by aws_vpc.default.main_route_table_id and defining the gateway defined by aws_internet_gateway.default.id<http://aws_internet_gateway.default.id> as being responsible for routing packets destined toward that route through the internet gateway.

An internet gateway sits as a bridge between the outside world and a public subnet in a VPC, allowing internet access in to your VPC.

Does that make things a little clearer?

Andrew

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