How to connect multiple Docker containers in AWS ElasticBeanstalk?

I have a Docker multicontainer configuration meant to run in a ElasticBeanstalk environment.

The EB environment runs in a VPC, in a public subnet, has a single load-balancer and a single instance bound.

It looks like all of the containers are running fine but they cannot communicate with each other even though i defined them as linked containers.

What do I need to do to get all of these containers talking to each other?

My Dockerrun.aws.json looks like this:

"containerDefinitions": 
    [
        {
            "name": "proxy",
            "image": "nginx",
            "essential": true,
            "memory": 128,
            "portMappings": 
            [
                {
                    "hostPort": 80,
                    "containerPort": 80
                }
            ],
            "links": 
            [
                "webapp"
            ],
            "mountPoints": 
            [
                {
                    "sourceVolume": "nginx-conf",
                    "containerPath": "/etc/nginx/conf.d",
                    "readOnly": true
                },
                {
                    "sourceVolume": "awseb-logs-proxy",
                    "containerPath": "/var/log/nginx"
                }
            ]
        },
        {
            "name": "webapp",
            "image": "jetty",
            "memory": 2048,
            "essential": true,
            "portMappings": 
            [
                {
                    "hostPort": 8080,
                    "containerPort": 8080
                }
            ],
            "links": 
            [
                "mongodb"
            ],
            "mountPoints": 
            [
                {
                    "sourceVolume": "jetty-webapp",
                    "containerPath": "/var/lib/jetty/webapps",
                    "readOnly": false
                },
                {
                    "sourceVolume": "awseb-logs-webapp",
                    "containerPath": "/var/log/jetty"
                }
            ]
        },
        {
            "name": "mongodb",
            "image": "mongo",
            "memory": 1024,
            "essential": true,
            "portMappings": 
            [
                {
                    "hostPort": 27017,
                    "containerPort": 27017
                }
            ],
            "mountPoints": 
            [
                {
                    "sourceVolume": "mongodb-data",
                    "containerPath": "/data/db",
                    "readOnly": false
                }
            ]
        }
    ]