Gcp networking

GCP Networking

Design, implement, and secure network infrastructure on Google Cloud Platform.

When to Use

• Building VPC networks for new GCP projects or multi-project architectures
• Configuring firewall rules to control traffic between services
• Setting up Cloud NAT for outbound internet access from private instances
• Deploying load balancers for HTTP(S), TCP/UDP, or internal traffic
• Implementing Private Service Connect or Shared VPC

Prerequisites

• Google Cloud SDK (gcloud) installed and authenticated
• Compute Engine API enabled
• IAM role roles/compute.networkAdmin for network management

gcloud services enable compute.googleapis.com servicenetworking.googleapis.com

VPC Network Creation

gcloud compute networks create prod-vpc \
  --subnet-mode=custom --bgp-routing-mode=regional --mtu=1460

gcloud compute networks subnets create us-subnet \
  --network=prod-vpc --region=us-central1 --range=10.0.0.0/20 \
  --enable-private-ip-google-access --enable-flow-logs \
  --logging-flow-sampling=0.5

gcloud compute networks subnets create eu-subnet \
  --network=prod-vpc --region=europe-west1 --range=10.1.0.0/20 \
  --enable-private-ip-google-access --enable-flow-logs

# Subnet with secondary ranges for GKE
gcloud compute networks subnets create gke-subnet \
  --network=prod-vpc --region=us-central1 --range=10.2.0.0/20 \
  --secondary-range=pods=10.4.0.0/14,services=10.8.0.0/20 \
  --enable-private-ip-google-access

# Proxy-only subnet (required for regional L7 LBs)
gcloud compute networks subnets create proxy-only-subnet \
  --network=prod-vpc --region=us-central1 --range=10.129.0.0/23 \
  --purpose=REGIONAL_MANAGED_PROXY --role=ACTIVE

Firewall Rules

gcloud compute firewall-rules create allow-http-https \
  --network=prod-vpc --allow=tcp:80,tcp:443 \
  --source-ranges=0.0.0.0/0 --target-tags=http-server --priority=1000

gcloud compute firewall-rules create allow-internal \
  --network=prod-vpc --allow=tcp,udp,icmp \
  --source-ranges=10.0.0.0/8 --priority=1000

gcloud compute firewall-rules create allow-iap-ssh \
  --network=prod-vpc --allow=tcp:22 \
  --source-ranges=35.235.240.0/20 --priority=1000

gcloud compute firewall-rules create allow-health-checks \
  --network=prod-vpc --allow=tcp:80,tcp:443,tcp:8080 \
  --source-ranges=130.211.0.0/22,35.191.0.0/16 \
  --target-tags=http-server --priority=900

# List firewall rules
gcloud compute firewall-rules list --filter="network=prod-vpc" \
  --format="table(name,direction,priority,allowed[].map().firewall_rule().list():label=ALLOW)"

Cloud NAT

gcloud compute routers create prod-router \
  --network=prod-vpc --region=us-central1

gcloud compute routers nats create prod-nat \
  --router=prod-router --region=us-central1 \
  --nat-all-subnet-ip-ranges --auto-allocate-nat-external-ips \
  --min-ports-per-vm=256 --max-ports-per-vm=4096 \
  --enable-logging --log-filter=ERRORS_ONLY

# Static NAT IPs (stable egress)
gcloud compute addresses create nat-ip-1 nat-ip-2 --region=us-central1
gcloud compute routers nats create prod-nat-static \
  --router=prod-router --region=us-central1 \
  --nat-all-subnet-ip-ranges --nat-external-ip-pool=nat-ip-1,nat-ip-2

External HTTP(S) Load Balancer

gcloud compute addresses create web-lb-ip --global

gcloud compute health-checks create http web-hc \
  --port=80 --request-path=/healthz --check-interval=10s --timeout=5s

gcloud compute backend-services create web-backend \
  --protocol=HTTP --port-name=http --health-checks=web-hc \
  --global --enable-cdn --enable-logging

gcloud compute backend-services add-backend web-backend \
  --instance-group=web-mig --instance-group-region=us-central1 \
  --balancing-mode=UTILIZATION --max-utilization=0.8 --global

gcloud compute url-maps create web-url-map --default-service=web-backend

gcloud compute ssl-certificates create web-cert \
  --domains=app.example.com --global

gcloud compute target-https-proxies create web-proxy \
  --url-map=web-url-map --ssl-certificates=web-cert

gcloud compute forwarding-rules create web-https \
  --address=web-lb-ip --target-https-proxy=web-proxy --ports=443 --global

Internal Load Balancer

gcloud compute backend-services create internal-backend \
  --protocol=TCP --region=us-central1 \
  --health-checks=web-hc --health-checks-region=us-central1 \
  --load-balancing-scheme=INTERNAL

gcloud compute forwarding-rules create internal-lb \
  --region=us-central1 --load-balancing-scheme=INTERNAL \
  --network=prod-vpc --subnet=us-subnet \
  --backend-service=internal-backend --ports=8080

Cloud Armor (DDoS and WAF)

gcloud compute security-policies create web-armor

gcloud compute security-policies rules create 1000 \
  --security-policy=web-armor \
  --expression="origin.region_code == 'XX'" --action=deny-403

gcloud compute security-policies rules create 2000 \
  --security-policy=web-armor --expression="true" \
  --action=rate-based-ban \
  --rate-limit-threshold-count=100 \
  --rate-limit-threshold-interval-sec=60 --ban-duration-sec=600

gcloud compute backend-services update web-backend \
  --security-policy=web-armor --global

Private Service Connect

gcloud compute addresses create psc-google-apis \
  --global --purpose=PRIVATE_SERVICE_CONNECT \
  --addresses=10.255.255.254 --network=prod-vpc

gcloud compute forwarding-rules create psc-google-apis \
  --global --network=prod-vpc --address=psc-google-apis \
  --target-google-apis-bundle=all-apis

Shared VPC

gcloud compute shared-vpc enable $HOST_PROJECT_ID
gcloud compute shared-vpc associated-projects add $SERVICE_PROJECT_ID \
  --host-project=$HOST_PROJECT_ID

Terraform Configuration

resource "google_compute_network" "vpc" {
  name                    = "prod-vpc"
  auto_create_subnetworks = false
  routing_mode            = "REGIONAL"
}

resource "google_compute_subnetwork" "us" {
  name                     = "us-subnet"
  ip_cidr_range            = "10.0.0.0/20"
  region                   = "us-central1"
  network                  = google_compute_network.vpc.id
  private_ip_google_access = true
  log_config { aggregation_interval = "INTERVAL_5_SEC"; flow_sampling = 0.5 }
}

resource "google_compute_firewall" "allow_http" {
  name    = "allow-http-https"
  network = google_compute_network.vpc.name
  allow { protocol = "tcp"; ports = ["80", "443"] }
  source_ranges = ["0.0.0.0/0"]
  target_tags   = ["http-server"]
}

resource "google_compute_firewall" "allow_iap" {
  name    = "allow-iap-ssh"
  network = google_compute_network.vpc.name
  allow { protocol = "tcp"; ports = ["22"] }
  source_ranges = ["35.235.240.0/20"]
}

resource "google_compute_router" "router" {
  name    = "prod-router"
  region  = "us-central1"
  network = google_compute_network.vpc.id
}

resource "google_compute_router_nat" "nat" {
  name                               = "prod-nat"
  router                             = google_compute_router.router.name
  region                             = "us-central1"
  nat_ip_allocate_option             = "AUTO_ONLY"
  source_subnetwork_ip_ranges_to_nat = "ALL_SUBNETWORKS_ALL_IP_RANGES"
  min_ports_per_vm                   = 256
  log_config { enable = true; filter = "ERRORS_ONLY" }
}

resource "google_compute_security_policy" "waf" {
  name = "web-armor"
  rule {
    action   = "deny(403)"
    priority = 1000
    match { expr { expression = "evaluatePreconfiguredExpr('xss-v33-stable')" } }
  }
  rule {
    action   = "allow"
    priority = 2147483647
    match { versioned_expr = "SRC_IPS_V1"; config { src_ip_ranges = ["*"] } }
  }
}

Common Operations

gcloud compute networks list
gcloud compute networks subnets list --network=prod-vpc
gcloud compute networks subnets describe us-subnet --region=us-central1
gcloud network-management connectivity-tests create test-web-to-db \
  --source-instance=projects/${PROJECT_ID}/zones/us-central1-a/instances/web \
  --destination-instance=projects/${PROJECT_ID}/zones/us-central1-a/instances/db \
  --destination-port=5432 --protocol=TCP

Troubleshooting

Symptom	Cause	Fix
Instance cannot reach internet	No external IP and no Cloud NAT	Configure Cloud NAT on the subnet's router
Firewall rule not taking effect	Wrong target tags or priority	Verify tags match instance; check priority ordering
Load balancer returns 502	Backend failing health checks	Check health check path/port; allow 130.211.0.0/22, 35.191.0.0/16
Cannot reach Google APIs from private VM	Private Google Access disabled	Enable --enable-private-ip-google-access on subnet
Cloud NAT port exhaustion	Too many connections per VM	Increase --min-ports-per-vm; enable dynamic port allocation
Shared VPC project cannot create VMs	Missing compute.networkUser role	Grant roles/compute.networkUser on host project
SSL cert stuck PROVISIONING	DNS not pointing to LB IP	Update A record to reserved static IP; wait up to 60 min

Related Skills

• gcp-compute - Compute Engine instances that use VPC networks and firewall rules
• gcp-gke - GKE clusters deployed in VPC subnets with secondary ranges
• gcp-cloud-sql - Private IP database connectivity through VPC peering
• terraform-gcp - Provision networking resources with Infrastructure as Code