This topic provides answers to some frequently asked questions about Express Connect circuits.

Can I access virtual private clouds (VPCs) in different regions after my data center is connected to Alibaba Cloud through an Express Connect circuit?

Yes, you can access VPCs in all regions after your data center is connected to Alibaba Cloud through an Express Connect circuit.

What types of ports does Alibaba Cloud Express Connect support?

The access devices of Alibaba Cloud support optical ports and copper Ethernet ports. By default, Alibaba Cloud provides LC optical transceiver modules with 1 Gbit/s and 10 Gbit/s optical ports. This type of optical transceiver module supports a maximum transmission distance of 10 km. To use optical transceiver modules that support a longer distance of data transmission, you must purchase them from a third-party service provider.

What is the highest bandwidth limit of an Express Connect circuit?

The highest bandwidth limit of an Express Connect circuit for which you can apply in the console is 10 Gbit/s. You can Submit a ticket to request higher bandwidth.

Do Express Connect circuits support dynamic routing protocols?

Yes, Express Connect circuits support Border Gateway Protocol (BGP).

Can I configure multiple Express Connect circuits to achieve disaster recovery?

Yes, you can use at most four Express Connect circuits to configure equal-cost multi-path routing (ECMP).

Can I connect an Express Connect circuit to multiple VPCs?

Yes, you can connect an Express Connect circuit to multiple VPCs. You must use Cloud Enterprise Network (CEN) to connect these VPCs with your data center.

How many VPCs can be connected to an Express Connect circuit?

The number of VPCs that can be connected to an Express Connect circuit depends on the maximum number of VPCs that can be attached to a CEN instance. By default, you can attach one virtual border router (VBR) and nine VPCs to a CEN instance. Therefore, each Express Connect circuit can connect to at most nine VPCs.

Can I extend a VLAN from a data center to a VPC through an Express Connect circuit?

No, you cannot extend a VLAN from a data center to a VPC through an Express Connect circuit. Alibaba Cloud supports only interconnections with external networks over Layer 3.

When I connect an Express Connect circuit to multiple VPCs, are these connections isolated from each other?

To isolate the connections, assign a VLAN ID to each connection. For more information, see Create a VBR.

Do Express Connect circuits support network address translation (NAT)?

No, Express Connect circuits do not support NAT. If your workloads require NAT, you must configure NAT in your data center.

What is the correlation between zones and access points?

Both zones and access points are scoped to regions. You can access all of the zones in a region from an access point in the same region.

If the access point that you choose and the VPC to be accessed are deployed in different regions, you must use CEN.

If the Elastic Compute Service (ECS) instance is deployed in Zone A, which access point can I choose?

You can choose any access point in the region to which Zone A belongs.

By default, the network latency of connections between different zones within the same region is less than 5 milliseconds. If you want to minimize the network latency, you can Submit a ticket to query the access point closest to Zone A.

How much does it cost to connect to Alibaba Cloud through an Express Connect circuit?

When you connect your data center to Alibaba Cloud through an Express Connect circuit, you are charged by Alibaba Cloud and your connectivity provider. For more information, see Billing.

How do I connect a data center to Alibaba Cloud through an Express Connect circuit?

1. Read the Express Connect user guide. 2. Choose an access point. 3. Apply for an Express Connect circuit and pay the initial installation fee in the console. 4. Apply for a Letter of Authorization (LOA). 5. Contact your connectivity provider to install the Express Connect circuit. 6. After your connectivity provider completes the installation, update the progress in the console and wait for Alibaba Cloud to install the pigtail. 7. Pay the resource usage fee. 8. Enable the Express Connect circuit. 9. Create a VBR. 10. Attach the VBR to a CEN instance, or create a peering connection. 11. Configure routes. 12. Run a ping test to verify the network connectivity between your data center and the VPC.

What are the requirements on IP addresses that are used to establish a connection over an Express Connect circuit?

When you specify IP addresses for a connection over an Express Connect circuit, make sure that the following requirements are met:

  • The IP address of the gateway on Alibaba Cloud and the IP address of the gateway device in the data center cannot conflict with each other. You can specify only private IP addresses. If public IP addresses are used in the data center, Submit a ticket to configure IP address mapping.
  • To prevent IP address conflicts, you cannot specify IP addresses from 100.64.0.0/10 for the gateway device in the data center.

What is a VLAN ID of a VBR?

  • If the VLAN ID is set to 0, the switch port of the VBR is a Layer 3 router interface instead of a VLAN interface. When a Layer 3 router interface is used, each Express Connect circuit corresponds to a VBR. In this case, you can connect the Express Connect circuit only to VPCs that belong to your account.
  • If the VLAN ID is set to a value from 1 to 2999, the switch port of the VBR is a Layer 3 VLAN subinterface. When a Layer 3 VLAN subinterface is used, each VLAN ID corresponds to a VBR. In this case, you can connect the Express Connect circuit to VPCs that belong to different accounts.

For example, a company has multiple subdivisions or subsidiaries. Each subdivision or subsidiary has a separate Alibaba Cloud account. Each Alibaba Cloud account owns a VPC. Before the company connects its subdivisions or subsidiaries to Alibaba Cloud through an Express Connect circuit, the company must assign a VLAN ID to each subdivision or subsidiary. When the company creates VBRs, the company must specify different VLAN IDs for the VBRs used by different subdivisions or subsidiaries.

What are the Alibaba Cloud-side and data center-side IP addresses specified on a VBR?

The Alibaba Cloud-side IP address is the IP address of the VBR. The data center-side IP address is the IP address of the gateway device in the data center. This allows your data center and the VPC to communicate with each other. When you create the VBR, make sure that the IP addresses that you specify belong to the same CIDR block.

How do I verify the network connectivity of an Express Connect circuit?

After your connectivity provider installs the Express Connect circuit in the Alibaba Cloud data center, the following tasks must be performed:

  1. Log on to the Express Connect console.
  2. In the top navigation bar, select the region and click Exclusive Physical Connection in the left-side navigation pane.
  3. On the Physical Connections page, click Confirm Delivery.

    The status of the Express Connect circuit changes to Waiting for Pigtail Installation. Alibaba Cloud will complete the pigtail installation within one to two business days. Then, the status of the Express Connect circuit changes to Pending for Payment.

  4. After you pay the resource usage fee, the status of the Express Connect circuit changes to Enabled.
  5. Then, create a VBR and configure routes.
  6. Run the ping command to verify the network connectivity between the data center and the VPC.

How do I connect a data center to an internal endpoint of an Object Storage Service (OSS) bucket in a VPC?

Internal OSS endpoints belong to 100.64.0.0/10, which is reserved by Alibaba Cloud. Therefore, you cannot add a 100.64.0.0/10 route to the VBR. You can divide 100.64.0.0/10 into smaller subnets. For example, 100.64.0.0/11 and 100.96.0.0/11. Then, you can add the routes to the VBR and set the next hop to the VPC.

What do I do if my data center cannot access the Elastic Compute Service (ECS) instance on Alibaba Cloud?

For more information about how to troubleshoot the issues, see Troubleshooting.

What do I do if my Express Connect circuit is down?

Ping the IP address of the VBR from the gateway device your the data center. If the gateway device in the data center fails to reach the specified IP address, report the issue to your connectivity provider. You can also Submit a ticket to Alibaba Cloud to check the access device connected to the Express Connect circuit.

If the access device in the Alibaba Cloud data center works as expected but the issue persists, you must notify your connectivity provider.

What do I do if the bandwidth cannot reach the specified bandwidth limit?

If the bandwidth limit of your router interface is lower than 1 Gbit/s, use iPerf3 to measure the bandwidth. If the bandwidth does not exceed 10 Mbit/s, check whether the half duplex mode is enabled for one of the ports. You can request your connectivity provider to switch the negotiation mode to adaptive.

If the bandwidth limit of your router interface is higher than 1 Gbit/s, the bandwidth of each data stream is limited to 130 Mbit/s or 250 Mbit/s when network traffic is distributed across multiple resources.

What do I do if the system returns an error when I add routes to or delete routes for a VBR?

The number of requests that the hardware of a VBR can process at a time is limited. You can add or delete routes after the ongoing tasks are completed.

What do I do if the token error is returned when I add routes?

The system returns the error when the cookie of your browser times out. Log out and try again later.