Limitations

Resource limits

Express Connect resource limits are managed through Quotas.

Network requirements

When connecting a data center to Alibaba Cloud with Express Connect, ensure that your cloud and on-premises CIDR blocks do not conflict. Your data center network must also meet these requirements:

• For optical fiber connections, use a single-mode optical module with one of the following specifications. Ensure identical optical module parameters at both ends.

  • 1000BASE-LX Ethernet single-mode optical module

  • 10GBASE-LR Ethernet single-mode optical module

  • 40GBASE-LR Ethernet single-mode optical module

  • 100GBASE-LR Ethernet single-mode optical module

• You must disable port auto-negotiation and manually configure the port speed and full-duplex mode.

• All devices in the connection path, including intermediate devices, must support 802.1Q VLAN encapsulation.

• Your on-premises network equipment must support Border Gateway Protocol (BGP) with BGP MD5 authentication, or static routing.

• In redundant connection scenarios, your devices must support route weight configuration.

• The physical connection layer must support a maximum transmission unit (MTU) of 1,500 bytes.

• We recommend using non-conflicting private IP addresses for your cloud and on-premises networks.

• Do not use 100.64.0.0/10 for your on-premises network. This range is reserved for Alibaba Cloud internal services and causes address conflicts.

• VBR-to-data-center interconnect addresses cannot use the 100.64.0.0/10 CIDR block.

• Configure your data center gateway to allow more than 500 ICMP ECHO REQUEST packets per second. Rate-limiting health check probes disrupts connectivity and causes network jitter.

Alibaba Cloud-side rate limits

Beyond the express connect circuit bandwidth limit, VPC-to-data-center traffic is subject to these rate limits:

• The maximum read/write throughput for OSS is 10 Gbps.

• For reliability, Express Connect enforces these bandwidth limits on a single hashed traffic flow from a VPC to a VBR:

  • If the configured bandwidth of the VBR or VBR-to-VPC connection is less than or equal to 1 Gbps, the rate limit equals the configured bandwidth.

  • If the configured bandwidth of the VBR or VBR-to-VPC connection is greater than 1 Gbps, the rate limit is 1/4 of the configured bandwidth. For example, if the bandwidth from the VPC to the VBR is 2 Gbps, the maximum bandwidth for a single hashed traffic flow is 500 Mbps.

    Note

    • The rate limit is based on the VBR bandwidth for CEN or ECR connections, and on the VBR-to-VPC connection bandwidth for VBR-to-VPC connections.

    • The VBR-to-VPC connection feature is not enabled by default. To use this feature, contact your account manager.

  A hashed traffic flow is defined by a five-tuple: source IP, source port, protocol, destination IP, and destination port. For example, 192.168.1.1 10000 TCP 121.XX.XX.76 80 is one hashed traffic flow — a TCP connection from 192.168.1.1:10000 to 121.XX.XX.76:80.

Express connect circuit limits

• Plan non-overlapping CIDR blocks for your VPC and on-premises data center before using Express Connect.

• The 100.64.0.0/10 CIDR block is reserved for internal cloud services. Your data center CIDR block must not overlap with this range.

• By default, Alibaba Cloud provides single-mode optical modules (1/10/40/100 Gbps) with a 10 km transmission distance.

• An express connect circuit does not support VXLAN traffic (UDP destination port 4789).

Redundant connection limits

• Alibaba Cloud guarantees service availability only when multiple express connect circuits connect to different access points. Single circuits or multiple circuits at the same access point do not qualify.

• Configure a health check when using two express connect circuits for redundancy. Without it, a physical connection failure disrupts your services.

Hosted connection limits

• Custom port configurations are not supported.

• Total allocated bandwidth for hosted connections must not exceed the underlying express connect circuit bandwidth.

• Users with reseller accounts cannot apply to become a Network Service Provider (NSP).

Installation requirements

• When entering an Alibaba Cloud data center, installation providers must comply with construction regulations from the data center operator and Alibaba Cloud engineers. Non-compliance prevents installation completion.

• If you purchase optical ports, instruct your carrier to connect to the Alibaba Cloud express connect circuit port using fiber optic cables.

• Alibaba Cloud prohibits the installation and colocation of optical-to-electrical conversion devices in its data centers.

• Network lockdowns mandated by policy or Alibaba Group may delay installation. Contact your account manager if affected.

• Access-point data centers are operated by telecom carriers or third-party providers, not Alibaba Cloud. You are responsible for their building access and in-building cabling fees.

Installation timelines

Timelines for Express Connect installation services: