google_compute_interconnect_attachment cost estimation
A VLAN attachment connecting your VPC to a Cloud Interconnect, billed per hour by capacity. A 1 Gbps attachment is ~$75/month, plus egress over the link.
A google_compute_interconnect_attachment (VLAN attachment) links a VPC to a Cloud Interconnect — Dedicated or Partner — to extend an on-premises network into Google Cloud. Cost is a per-hour fee set by the attachment's capacity, charged continuously, plus egress data transfer over the interconnect (billed at the lower interconnect egress rate, not internet egress).
A 1 Gbps attachment is ~$0.10282/hour, about $75/month; a 10 Gbps attachment is ~$0.7534/hour, ~$550/month. For Dedicated Interconnect there's also the underlying interconnect circuit/port cost (a separate resource); for Partner Interconnect the partner bills the connection and the attachment capacity sets the GCP-side rate.
The standing attachment fee is the predictable part; egress over the link is the variable one. The cost decisions are the capacity you provision (match to actual throughput needs) and how many attachments you run for redundancy.
c3x prices the attachment from its bandwidth, so the standing monthly cost is visible before deployment; egress is usage-driven.
Terraform example
A minimal but realistic configuration that C3X can estimate.
resource "google_compute_interconnect_attachment" "onprem" {
name = "onprem-vlan"
type = "PARTNER"
router = google_compute_router.interconnect.id
bandwidth = "BPS_1G"
edge_availability_domain = "AVAILABILITY_DOMAIN_1"
}Pricing dimensions
What you actually pay for when you provision google_compute_interconnect_attachment.
| Dimension | Unit | What's being charged |
|---|---|---|
| VLAN attachment | per hour | Per-hour fee set by the attachment's capacity (bandwidth), charged continuously. $0.10282/hour for 1 Gbps → ~$75.06/month; 10 Gbps ~$550/month |
| Interconnect egress | per GB | Data egressing over the interconnect bills at the interconnect egress rate (lower than internet egress). Usage-based. |
Sample C3X output
A 1 Gbps VLAN attachment running 24/7 (attachment fee only; add egress):
google_compute_interconnect_attachment.onprem
└─ VLAN attachment (1 Gbps) 730 hours $75.06
Monthly $75.06Optimization tips
Common ways to reduce google_compute_interconnect_attachment cost without changing the workload.
Right-size the attachment capacity
Difference between capacity tiersThe per-hour fee scales with bandwidth — a 10 Gbps attachment is ~7x a 1 Gbps one. Provision the capacity your actual throughput needs, not the maximum; you can resize as demand grows.
Balance redundancy against cost
~$75+/month per redundant attachment avoidedProduction interconnects often run two attachments across availability domains for resilience, doubling the attachment fee. Right for critical connectivity; for non-critical or dev links, a single attachment halves the standing cost.
Prefer interconnect egress over internet egress for hybrid traffic
Per-GB rate difference on hybrid trafficEgress over the interconnect is cheaper than internet egress. Routing on-prem-bound traffic over the interconnect rather than the public internet both lowers the per-GB rate and improves latency.
Consider Partner Interconnect for sub-10G needs
Avoids Dedicated port over-commitmentPartner Interconnect offers smaller capacity increments (50 Mbps-10 Gbps) without the full Dedicated Interconnect port commitment, fitting smaller hybrid connectivity needs more cost-effectively.
FAQ
How is a GCP Interconnect VLAN attachment billed?
A per-hour fee by capacity, charged continuously — ~$75/month for 1 Gbps, ~$550/month for 10 Gbps — plus egress data transfer over the interconnect at the (cheaper-than-internet) interconnect egress rate. Dedicated Interconnect also has a separate circuit/port cost.
Why run two attachments?
Redundancy. Production hybrid connectivity often uses two attachments across edge availability domains so a single failure doesn't sever the link — at double the attachment fee. Single attachments suit non-critical or dev connectivity.
How does c3x estimate the cost?
From the bandwidth attribute, pricing the standing per-hour attachment fee. Egress over the interconnect is usage-driven and modelled separately.
Related resources
Estimate this resource in your own Terraform
Free, open source, no API key. C3X parses your Terraform and shows line-item cost for every resource, including google_compute_interconnect_attachment.