Networking

No internet egress requires a VPC without an internet gateway (IGW) or NAT gateway. Attach that VPC through a custom network connector. Audit the selected subnet routes for other internet paths, including IPv6 gateways, transit networks, peering, and proxies. Private services and VPC endpoints remain reachable if your VPC configuration permits them.

Omitting the managed INTERNET_EGRESS connector does not disable internet access on the default MicroVM network. --deny-egress only sets proxy variables; a workload can ignore them. Neither is an isolation boundary.

Create a VPC connector

The Lambda core API manages connectors separately from the lambda-microvms API. Use a current boto3 release to create and manage connectors. This package accepts existing connector ARNs at launch; it does not manage the connectors’ lifecycle.

Provision the VPC, subnets, security groups, and a Lambda connector operator role first. The operator role needs permissions to manage the connector’s network interfaces; it is separate from the VM execution role. The following example creates a real AWS resource:

import os
import time
import uuid

import boto3

core = boto3.client("lambda-core", region_name="us-east-1")
connector = core.create_network_connector(
    Name="isolated-microvms",
    ClientToken=str(uuid.uuid4()),
    OperatorRole=os.environ["CONNECTOR_OPERATOR_ROLE_ARN"],
    Configuration={
        "VpcEgressConfiguration": {
            "SubnetIds": [os.environ["ISOLATED_SUBNET_ID"]],
            "SecurityGroupIds": [os.environ["CONNECTOR_SECURITY_GROUP_ID"]],
            "NetworkProtocol": "IPv4",
            "AssociatedComputeResourceTypes": ["MicroVm"],
        }
    },
)
arn = connector["Arn"]
deadline = time.monotonic() + 900
while True:
    status = core.get_network_connector(Identifier=arn)
    if status.get("State") == "ACTIVE":
        break
    if status.get("State") != "PENDING":
        raise RuntimeError(status.get("StateReason", status.get("State")))
    if time.monotonic() >= deadline:
        raise TimeoutError(f"Connector still pending: {arn}")
    time.sleep(5)
print(arn)

Creation is asynchronous and there is no built-in boto3 waiter. Preserve the client token when retrying the same creation request. After updates, inspect LastUpdateStatus as well as State; an active connector can have a failed configuration update. Delete an unused connector explicitly with delete_network_connector(Identifier=arn) and confirm completion.

Attach it at launch

microvm run --image my-image \
  --egress-network-connector "$CONNECTOR_ARN" \
  --exec "echo hello"

Persist the list in microvm.toml as egress-network-connectors = ["ARN"]. Explicit flags replace that configured list. The flag is repeatable up to the API’s connector limit. Do not combine it with --egress, which selects the managed internet connector. Python launch methods accept egress_network_connectors=[arn]; Node launch options use egressNetworkConnectors: [arn]. The AWS wire field is egressNetworkConnectors on RunMicrovm.

An attached connector ARN is not proof of isolation. The package does not audit its VPC, route tables, or security groups. Verify public destinations are unreachable from the launched VM and private destinations behave as intended. Custom connectors and VPC resources are managed separately from VM cleanup.

The VM execution role remains available through guest metadata. Restrict that role even when the VPC has no internet route; see Trust.

Evidence

Reviewed 2026-09-16 against boto3/botocore 1.43.95, Lambda core API version 2026-04-30, and MicroVM API version 2025-09-09. Connector configuration and state transitions above come from AWS documentation and SDK models. The example passed boto3 parameter validation with stubbed responses; it was not live-executed during this documentation refresh. Earlier default-network measurements are retained in Platform.