Google Cloud Router: Definition, use cases, troubleshooting, and more

In the intricate world of Google Cloud Platform (GCP), seamless network connectivity and intelligent traffic management are foundational to building scalable, secure, and high-performing cloud architectures. Google Cloud Router plays a pivotal role in achieving this by enabling dynamic routing between cloud resources and external networks.

This guide covers everything you need to know about Google Cloud Router. Whether you're just getting started or looking for troubleshooting tips for a complex routing issue, you'll find practical insights and solutions here.

An overview of Google Cloud Router

Google Cloud Router is a GCP service that enables dynamic Border Gateway Protocol (BGP) routing between your Virtual Private Cloud (VPC) networks and external networks. Examples of external networks can be on-premises data centers, other cloud providers, other VPC networks, or third-party networks. Since Cloud Router dynamically updates routes based on network changes, there’s no need for network administrators to make any manual adjustments (to static routes).

How does it work?

Cloud Router manages dynamic routing in a VPC network using BGP tasks, a dynamic route control plane, and VPC network control and data planes. Regional BGP tasks establish and manage BGP sessions, in which route prefixes are exchanged with peer routers.

These tasks feed information to the dynamic route control plane, which aggregates and distributes routing data. In global dynamic routing, control planes across regions communicate to ensure consistent routing.

The VPC network control plane receives learned routes and programs them into the network, while the VPC data plane forwards packets based on these routes. This architecture enables automated, scalable, and efficient routing between Google Cloud and external networks.

Key features

Here are some of Cloud Router’s top features:

• BGP session management: In addition to enabling BGP sessions with peer networks, cloud router also includes support for Bidirectional Forwarding Detection (BFD) to detect network failures quickly and MD5 authentication for securing BGP sessions.
• Advertised routes: Cloud Router can advertise specific IP ranges to connected networks when used with supported services like Dedicated Interconnect and Classic/HA VPN. This allows external networks to recognize and route traffic to the advertised destinations.
• Learned routes: Cloud Router automatically learns routes from BGP peers and creates dynamic routes in VPC networks. This means that routing continues seamlessly even when network conditions change.
• BGP route policies: These policies allow you to filter incoming and outgoing BGP routes or modify route attributes like AS path, local preference, and MED (Multi-Exit Discriminator) to control routing decisions. This granular control can be used to implement different use cases, such as unwanted route prevention and load balancing.

Google Cloud Router use cases

Cloud Router’s versatile networking capabilities enable a range of business use cases, such as:

• Multi-cloud network integration: Enable cross-cloud communication by peering Cloud Router with AWS Transit Gateway or Azure Virtual WAN. A global enterprise may use BGP route policies to prioritize traffic to GCP for analytics workloads while directing backups to another cloud provider.
• Disaster Recovery (DR): Automatically redirect traffic to GCP during on-premises outages by advertising backup routes via Cloud Router. For example, a financial institution can failover its trading systems to GCP in minutes, with BGP dynamically updating paths to maintain uptime.
• SaaS application optimization: Improve performance for SaaS tools (e.g., Salesforce, Microsoft 365) by routing traffic over private connections. For instance, a healthcare provider could use Cloud Router to advertise SaaS IP ranges to its VPC. This would ensure low-latency access and avoid potential security risks associated with the public internet.
• Network segmentation for compliance: Isolate sensitive workloads using custom route policies. For example, a company handling PCI DSS data could use Cloud Router policies to ensure that traffic from its payment processing environment is routed exclusively through dedicated, compliant connections.

Benefits of using Google Cloud Router

Next, let’s discuss some tangible advantages of incorporating Cloud Router into your infrastructure:

• Efficient multi-region routing: With global dynamic routing mode, traffic flows freely across Google Cloud regions without the need for any static route management.
• Optimized traffic flow: By advertising and learning routes in real time, Cloud Router enables better load balancing and efficient traffic distribution. This improves the performance of the overall network.
• Security and control: Features like MD5 authentication for BGP sessions and BGP route policies allow organizations to enforce security rules and control how traffic flows between networks.
• Scalability: When new subnets or resources are added to the network, Cloud Router automatically updates routes. This ensures smooth and hassle-free expansion.
• Future-proof architecture: With Cloud Router, your infrastructure remains future-proof, as you can integrate it with new networks and cloud platforms whenever needed and without requiring major changes.

Google Cloud Router troubleshooting guide

Google Cloud Router, like any feature-rich networking platform, can encounter issues related to performance, connectivity, and scalability. This section dissects the most common problems and shares troubleshooting advice for each.

Connectivity issues

Let’s start with connectivity issues that can disrupt communication between your core networks.

BGP session not establishing

The BGP session between Cloud Router and the peer device is not coming up.

Symptoms:

• Peer router shows BGP session as "Idle" or "Active". It never reaches an "Established" state.
• Routes are not being exchanged between Cloud Router and the peer.

Troubleshooting:

• Ensure that the BGP peer IP and ASN (Autonomous System Numbers) are correctly configured on both Cloud Router and the peer device.
• Verify that firewall rules allow the TCP port being used for BGP communication.
• Check if the peer router is reachable via Cloud Interconnect or VPN.
• Confirm that MD5 authentication settings match on both sides (if enabled).

No routes being advertised

Cloud Router is not advertising routes to the peer.

Symptoms:

• The peer router does not receive any routes from Cloud Router.
• BGP session is established, but the routing table remains empty.

Troubleshooting:

• Verify that advertised route prefixes are correctly configured in Cloud Router.
• Ensure that your BGP route policies are not inadvertently filtering out routes required for proper network communication.
• Ensure that the VPC subnet is set to export routes dynamically.
• Confirm that the peer router supports and accepts the advertised routes.

Intermittent connectivity loss

Cloud Router connections randomly drop and reconnect.

Symptoms:

• Traffic occasionally fails between on-premises and cloud networks.
• Cloud Router logs show repeated session resets.

Troubleshooting:

• Check for any network congestion that could be affecting BGP sessions.
• Enable Bidirectional Forwarding Detection (BFD) to detect failures quickly.
• Ensure that peer devices are stable and not undergoing frequent reboots.
• Review Google Cloud network status for any ongoing outages.

Performance issues

Next, let’s discuss some common performance-related problems.

High Latency in routed traffic

Traffic routed through Cloud Router experiences unexpected delays.

Symptoms:

• Increased round-trip time (RTT) when pinging external resources.
• Slow application performance for workloads using Cloud Router.

Troubleshooting:

• Verify that the BGP path selection process is choosing the optimal route.
• Check whether network congestion is affecting inter-region or hybrid traffic.
• Use Cloud Monitoring and Cloud Trace to analyze packet flow and latency.
• Consider optimizing route policies to prefer lower-latency paths.
• Set up a dedicated monitoring tool, like Site24x7, to continuously monitor all critical metrics and proactively identify potential bottlenecks.

Asymmetrical routing

Inbound and outbound traffic follow different network paths.

Symptoms:

• Packets take different paths when entering and leaving the network.
• Increased packet loss or inconsistent network performance.

Troubleshooting:

• Check BGP route policies to ensure that they are not causing unintended path selection.
• Verify that advertised routes match expected inbound paths.
• Use traceroute and network flow logs to identify route mismatches.
• If needed, adjust local preference and AS path attributes to influence routing decisions.

Scalability issues

As your network infrastructure grows, you may face issues related to scalability. Let’s explore some of the more common ones:

Route limit exceeded

Cloud Router reaches the maximum allowed number of learned or advertised routes.

Symptoms:

• New routes are not being accepted or advertised.
• Logs show "Route quota exceeded" or similar errors.

Troubleshooting:

• Check Google Cloud route quotas to determine whether the limit has indeed been reached.
• Optimize routing by aggregating smaller prefixes into larger subnets.
• Remove unnecessary or stale routes to free up capacity.
• If necessary, request an increased route quota from Google Cloud support.

BGP session flapping

The BGP session frequently goes up and down, which is disrupting network stability.

Symptoms:

• Logs show repeated BGP session resets.
• Routes intermittently disappear and reappear in the routing table.

Troubleshooting:

• Enable Bidirectional Forwarding Detection (BFD) to quickly detect and stabilize session failures.
• Check network latency and jitter between Cloud Router and the peer.
• Verify that BGP keepalive and hold timers are properly configured.
• Investigate potential fluctuations in peer network availability.

Security issues

Since Cloud Router plays a key role in your network, it's important to stay aware of potential security risks. Here are some common security issues and how to fix them:

Unauthorized route advertisements

An external network is advertising routes that shouldn't be accepted.

Symptoms:

• Unexpected routes appear in Cloud Router's learned route table.
• Traffic is being redirected in unintended ways.

Troubleshooting:

• Apply BGP route filtering policies to block unwanted routes.
• Enable MD5 authentication to prevent unauthorized BGP sessions.
• Check Google Cloud IAM permissions to ensure that only authorized users can modify routing settings.
• If using RPKI (Resource Public Key Infrastructure), implement ROV (Route Origin Validation) to validate the origin of BGP routes. Configure Cloud Router to reject routes with invalid ROV status.
• Periodically review Cloud Router's learned route table to identify and remove any unauthorized or stale routes.

Unwanted traffic reaching the VPC

Cloud Router is allowing external traffic that should be blocked.

Symptoms:

• Unexpected inbound traffic from unapproved sources.
• Potential security breaches or data exfiltration.

Troubleshooting:

• Implement firewall rules to block unauthorized IP ranges.
• Verify that only required routes are advertised to external networks.
• Enable Google Cloud Threat Detection to monitor and block malicious traffic.
• Carefully examine all inbound and outbound BGP route policies. Incorrect policies can lead to unwanted route propagation. Pay close attention to AS path filtering, prefix lists, and other policy configurations.
• Enable VPC Flow Logs to capture detailed information about network traffic. Use Cloud Monitoring to set up alerts for unusual traffic patterns or spikes.

Misconfigured firewall rules

Improper firewall rules can expose your Cloud Router to unauthorized access and/or block necessary network traffic.

Symptoms:

• Unexpected network disruptions or unreachable services.
• Unauthorized access attempts detected in logs.

Troubleshooting:

• Review firewall rules to make sure that they allow necessary BGP traffic.
• Verify that no overly permissive rules expose Cloud Router to unwanted external access.
• Use IAM policies to restrict who can modify firewall rules.
• Regularly audit and update firewall settings based on security best practices.

Configuration Errors

Cloud Router misconfigurations can leave you vulnerable to cyberattacks. Let’s discuss some common ones:

Incorrect ASN configuration

The Cloud Router’s BGP ASN does not match the expected configuration.

Symptoms:

• BGP session fails to establish.
• Peer router rejects BGP connections due to ASN mismatch.

Troubleshooting:

• Verify that the ASN in Cloud Router matches the peer router's expected ASN.
• Ensure that the correct ASN type (public or private) is used.
• After correcting the ASN configuration, restart the BGP session on both the Cloud Router and the peer router to apply the changes.
• Check the BGP configuration logs on both the Cloud Router and the peer router for any error messages related to ASN mismatch.
• Verify that firewall rules on both the Cloud Router and the peer router are not blocking BGP traffic.

Overlapping subnet CIDR (Classless Inter-Domain Routing) blocks

Conflicting subnet ranges cause route conflicts.

Symptoms:

• Traffic fails to reach certain destinations.
• Cloud Router logs show "conflicting route" errors.

Troubleshooting:

• Check VPC subnet allocations and ensure that there are no overlaps.
• Modify BGP route advertisements to avoid conflicting prefixes.
• If overlapping IP addresses are unavoidable, use Private Google Access for on-premises hosts to access Google APIs and services without traversing the public internet. This will allow communication to google services without the need to route the overlapping addresses.
• Use Google Clouds Network Topology to visualize your network and identify overlapping subnets.

Getting started with Google Cloud Router

This section provides a quick start guide to setting up Google Cloud Router.

Before you can set up Cloud Router, you’ll need:

• A Google Cloud project with billing enabled.
• A VPC network where the Cloud Router will be deployed.
• A Cross-Cloud Interconnect or cloud VPN connection to establish BGP peering.
• Necessary IAM permissions.
• Access to the latest version of the Google Cloud CLI.

With the prerequisites sorted, follow these steps to create and configure Cloud Router:

1. In the Google Cloud Console, go to the Create a Cloud Router page.
2. Enter the details for the router, including a name, description, network, region, Google ASN, BGP peer keepalive interval, and BGP identifier.
3. If you want to enter any custom advertised routes, navigate to the Advertised routes section.
4. Otherwise, click Create. The router should now be available in the Cloud Router listing page.
5. Set up a network connectivity product. Available options are: dedicated interconnect, partner interconnect, cloud VPN, and router appliance.

Google Cloud Router best practices

To maximize the performance, reliability, and security of your network, you should adhere to the following best practices when configuring and managing Google Cloud Router.

• Enable global dynamic routing: If your setup involves multiple regions, enable global dynamic routing to allow seamless communication between VPCs across regions.
• Use BGP route policies for traffic control: Apply BGP route policies to filter routes, adjust priorities, and control how traffic flows between networks.
• Implement security measures: Use MD5 authentication for BGP sessions to prevent unauthorized route injections.
• Optimize route advertisements: Advertise only the necessary IP ranges to reduce unnecessary traffic and improve network efficiency.
• Monitor BGP sessions regularly: Use dedicated monitoring tools like Site24x7 to track the most crucial metrics, including BGP session health.
• Plan for high availability: Deploy multiple Cloud Routers in different regions to avoid a single point of failure in your network.
• Keep IAM permissions in check: Grant Cloud Router-related permissions only to authorized users to prevent accidental or malicious misconfigurations.
• Prefer private ASNs for internal use: Use private Autonomous System Numbers (ASNs) for internal routing within your organization. This avoids potential conflicts with public ASNs.
• Remove unauthorized/stale routes: Periodically review your Cloud Router's learned route table to identify and remove any unauthorized or stale routes.
• Maintain through documentation: Document your network topology, subnet allocations, and routing configurations. This simplifies troubleshooting and maintains consistency.
• Enable Bidirectional Forwarding Detection (BFD): BFD helps detect network failures faster, which helps maintain high availability and reduce downtime.
• Optimize AS path prepending: Direct traffic by making certain routes less desirable through AS path prepending.
• Test route failover scenarios: Regularly test failover mechanisms to confirm that backup routes and redundancy measures work as expected.
• Regularly review logs and alerts: Set up log-based alerts to proactively detect anomalies or unauthorized route changes. Dedicated monitoring tools like Site24x7 offer this functionality out of the box.
• Update network configurations in stages: When making changes, update configurations in phases to minimize the risk of disruptions.

Conclusion

Google Cloud Router is a powerful tool for managing dynamic routing between your Google Cloud environment and external networks. It simplifies network architecture, optimizes traffic flow, and delivers scalability as your infrastructure grows.

We hope that this guide has shown you how Cloud Router works, and helped you understand its benefits, common issues and troubleshooting steps, and best practices.