How to get instance's route table id using CLI?

Question

I'd like to find a route table id associated with the given EC2 instance.

How can this be achieved using AWS CLI?

---

I've tried to use aws ec2 describe-vpcs, but the route tables are not there.

I'm using aws-cli/1.11.13.

Answer 1

You can achieve this by determining which subnet the ec2 instance belongs to, then check which route table the subnet is associated with.

#!/bin/bash

instanceId='YOU-INSTANCE-ID'

#finds the subnetId that the instance belongs to
subnetId=$(aws ec2 describe-instances \
           --instance-id $instanceId \
           --query "Reservations[*].Instances[].SubnetId" \
           --output text)

routingTableId=$(aws ec2 describe-route-tables \
                 --query "RouteTables[*].Associations[?SubnetId=='$subnetId'].RouteTableId" \
                 --output text)

echo $routingTableId

Answer 2

The route table is associated with VPC, which is associated with the instance.

Given $id shell variable has the instance ID, e.g.

id=i-0xyz # Replace i-0xyz with the real Instance ID.

here is the shell command to get VPCs associated with the instance and assign to $vpcs variable:

vpcs=$(aws ec2 describe-instances --instance-id $id --query 'Reservations[].Instances[].NetworkInterfaces[].VpcId' --output text)

Then to list the route tables associated with VPC, run:

aws ec2 describe-route-tables --filters "Name=vpc-id,Values=$vpcs"

To get just the route ids, add: --query "RouteTables[].RouteTableId[]" parameter.