Troubleshooting

This troubleshooting guide can help you solve common issues that you might encounter when using Cloud Interconnect:

• General troubleshooting
• Dedicated Interconnect
• Partner Interconnect

For answers to common questions about Cloud Interconnect architecture and features, see the Cloud Interconnect FAQ.

For definitions of terms used on this page, see Cloud Interconnect key terms.

General troubleshooting

Can't connect to resources in other regions

By default, Virtual Private Cloud (VPC) networks are regional, meaning that Cloud Router advertises only the subnets in its region. To connect to other regions, set the dynamic routing mode of your VPC network to global so that Cloud Router can advertise all subnets.

For more information, see Dynamic routing mode in the Cloud Router documentation.

Can't ping Cloud Router

If you can't ping Cloud Router, find your product in the following table and perform the troubleshooting steps for that product.

Troubleshooting steps to follow	Dedicated Interconnect	Partner Interconnect with L3 partner	Partner Interconnect with L2 partner
For Partner Interconnect, the Cloud Router might never be pingable because some partners filter traffic to the IP range (169.254.0.0/16) for Cloud Router. For L3 partners, the partner automatically configures BGP. If BGP doesn't come up, contact your partner.	Not applicable	Yes	Not applicable
Verify that your local device has learned the correct MAC address for the Google Cloud side of the connection. For more information, see Troubleshooting ARP.	Yes	Not applicable	Not applicable
Verify that your Cloud Router has an interface and a BGP peer. Cloud Router is not pingable unless the interface and BGP peer are fully configured, including the remote ASN. For Dedicated Interconnect, see BGP session not working. For L2 Partner Interconnect, Google has added the interface and BGP peer for Cloud Router automatically, but you must configure the remote ASN.	Yes	Not applicable	Yes

Troubleshooting ARP

For Dedicated Interconnect, to find the correct MAC address, run the following gcloud command:

  gcloud compute interconnects get-diagnostics INTERCONNECT_NAME

The googleSystemID contains the MAC address that should be present in your device's ARP table for IP addresses assigned to Cloud Router.

  result:
    links:
    — circuitId: SAMPLE-0
      googleDemarc: sample-local-demarc-0
      lacpStatus:
        googleSystemId: ''
        neighborSystemId: ''
        state: DETACHED
      receivingOpticalPower:
        value: 0.0
      transmittingOpticalPower:
        value: 0.0
    macAddress: 00:00:00:00:00:00

If your device has not learned a MAC address, verify that the correct VLAN ID and IP address are configured on the subinterface.

For Partner Interconnect, if you see the wrong MAC address on your device, verify that you have not bridged the Layer 2 segments of two VLAN attachments. The Google Cloud side of the Interconnect connection is configured with ip proxy-arp, which replies to all ARP requests and can cause your on-premises router to learn incorrect ARP entries.

Can't create VLAN attachment

If you attempt to create a VLAN attachment for Dedicated Interconnect or Partner Interconnect that violates an organization policy, you see an error message. See the following example error message from running gcloud compute interconnects attachments partner create:

ERROR: (gcloud.compute.interconnects.attachments.partner.create) Could not fetch resource:
- Constraint constraints/compute.restrictPartnerInterconnectUsage violated for projects/example-project. projects/example-project/global/networks/example-network is not allowed to use the Partner Interconnect.

For more information, see Restricting Cloud Interconnect usage and contact your organization administrator.

Sharing connections with other projects in my organization

Use Shared VPC to share a connection, such as a VLAN attachment or a Dedicated Interconnect connection in a host project.

For more information about setting up a Shared VPC network, see Provisioning Shared VPC.

For more information about configuring attachments in a Shared VPC network, see Enabling multiple VPC networks to access the same VLAN attachment.

Dedicated Interconnect

Google can't ping you during the Interconnect connection provisioning process

Check that you're using the correct IP and LACP configuration. During the testing process, Google sends you different test IP configurations for your on-premises router, depending on whether you order a multiple-link bundle or a single-link bundle. Don't configure VLAN attachments for either of these tests.

For multiple-link bundles

• The first set of IP addresses that Google sends is for testing multi-circuit connectivity on each individual link. Configure the test IP addresses on every physical link (without LACP configured), as instructed in the emails that Google sent you. Google must ping all the IP addresses successfully before this first test passes.
• For the second test, remove all the IP addresses from the first test. Configure the port channel with LACP even if your connection has only one link. Google pings the port channel address. Don't modify the LACP configuration of your port channel after the connection has passed the final test. However, you must remove the test IP address from the port channel interface.

For single-link bundles

• Google sends the final production IP address for testing single-circuit connectivity. Configure the IP address on the bundle interface (with LACP configured, either active or passive mode), as instructed in the email that Google sent you. Google must ping the bundle interface IP address successfully before this test passes. Configure the port channel with LACP even if your connection has only one link.

Can't ping Cloud Router

• Check that you can ping Google's port channel IP address. The IP address is the googleIpAddress value when you view the Interconnect connection details.
• Check that you have the correct VLAN on your on-premises router's subinterface. The VLAN information should match the information provided by the VLAN attachment.
• Check that you have the right IP address on your on-premises router's subinterface. When you create a VLAN attachment, it allocates a pair of link-local IP addresses. One is for an interface on a Cloud Router (cloudRouterIpAddress), and the other is for a subinterface on your on-premises router's port channel, not the port channel itself (customerRouterIpAddress).
• If you're testing the performance of your VLAN attachments, don't ping Cloud Router. Instead, create and then use a Compute Engine virtual machine (VM) instance in your VPC network. For more information, see Performance testing.

BGP session not working

• Enable multi-hop BGP on your on-premises router with at least two hops.
• Check that you have the correct neighbor IP address configured on your on-premises router. Use the BGP peer IP address (cloudRouterIpAddress) that the VLAN attachment allocated.
• Check that the local ASN configuration on your on-premises router matches the peer ASN on the Cloud Router. In addition, check that the local ASN configuration on the Cloud Router matches the peer ASN on your on-premises router.

• Each attachment is allocated a unique /29 CIDR from 169.254.0.0/16 within your VPC network. One IP address in the /29 CIDR is allocated for the Cloud Router and the other for your on-premises router.

  Check that the correct IP addresses are allocated for your on-premises router interface and its BGP neighbor. A common mistake is to configure a /30 on your on-premises router interface instead of a /29. Google Cloud reserves all other addresses in the /29 CIDR.

  Make sure that you have not allocated any other IP addresses from this CIDR to the VLAN attachment interface on your router.

Can't reach VMs in your VPC network

• Check that you can ping the port channel and VLAN attachment.
• Check that your BGP session is active.
• Check that your on-premises router is advertising and receiving routes.
• Set the MTU size to 1440 or 1500 on your on-premises router, depending on the configuration of your VLAN attachment and VPC network.

Performance testing over your VLAN attachments

If you need to test the performance of your VLAN attachments, use a VM in your VPC network. Add the performance tools that you require on the VM. Don't use the Cloud Router link-local IP address to test for latency, such as ICMP ping or path MTU. Using Cloud Router can give unpredictable results.

Getting diagnostics

To get current, detailed technical information about the Google Cloud side of a Dedicated Interconnect connection on demand, see Getting diagnostics.

Partner Interconnect

BGP session not working (Layer 2 connections)

• Check that your on-premises router has been configured with a BGP session to your Cloud Routers.
• Enable multi-hop BGP on your on-premises router with at least two hops.
• Check that you have the correct neighbor IP address configured on your on-premises router. Use the BGP peer IP address (cloudRouterIpAddress) that the VLAN attachment allocated.
• Check that the local ASN configuration on your on-premises router matches the peer ASN on the Cloud Router (16550). In addition, check that the local ASN configuration on the Cloud Router matches the peer ASN on your on-premises router.

BGP session not working (Layer 3 connections)

• Your Cloud Router must be configured with your service provider's ASN. Contact your service provider for assistance.

Can't ping Cloud Router (Layer 2 connections)

• Check that you have the correct VLAN attachment on your on-premises router's subinterface. The VLAN attachment information should match the information provided by your service provider.
• Check that you have the right IP address on your on-premises router's subinterface. After your service provider configures your VLAN attachment, the attachment allocates a pair of link-local IP addresses. One is for an interface on the associated Cloud Router (cloudRouterIpAddress), and the other is for a subinterface on your on-premises router's port channel, not the port channel itself (customerRouterIpAddress).
• If you're testing the performance of your attachments, don't ping Cloud Router. Instead, create and then use a VM in your VPC network. For more information, see Performance testing.

Can't send and learn MED values over an L3 Partner Interconnect connection

If you are using a Partner Interconnect connection where a Layer 3 service provider handles BGP for you, Cloud Router can't learn MED values from your on-premises router or send MED values to that router. This is because MED values can't pass through autonomous systems. Over this type of connection, you can't set route priorities for routes advertised by Cloud Router to your on-premises router. In addition, you can't set route priorities for routes advertised by your on-premises router to your VPC network.

All other issues

For additional assistance, contact your service provider. If needed, your service provider will contact Google to fix issues related to the Google side of the network.