Built on Alibaba Cloud's Software Defined Network (SDN) architecture, a Virtual Border Router (VBR) is a virtualized physical port on an Express Connect circuit. A VBR serves as a router between your on-premises customer-premises equipment (CPE) and a Virtual Private Cloud (VPC), forwarding traffic between your Internet Data Center (IDC) and your VPC.
Like a VPC router, each VBR maintains a dedicated route table. Configure routes in the table to control traffic forwarding.
Features
A VBR provides the following capabilities:
Forwards data packets between a VPC and an on-premises IDC.
Supports two interface types for an Express Connect circuit: a Layer 3 router interface or a Layer 3 VLAN subinterface.
In Layer 3 subinterface mode, it recognizes or attaches Virtual Local Area Network (VLAN) tags.
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Supports Border Gateway Protocol (BGP).
BGP is a dynamic routing protocol based on TCP. It exchanges routing and network reachability information between different autonomous systems (AS). Using BGP with Express Connect lets you connect your on-premises IDC to a VBR, helping you build a more efficient, flexible, and reliable hybrid cloud.
A VBR supports both IPv4 and IPv6 BGP sessions.
Limitations
Source address-based policy-based routing is not supported.
Each VBR has exactly one route table.
BGP version 4 (BGP-4) is the only supported BGP version.
Each VBR supports a maximum of eight BGP peers.
Each BGP peer supports a maximum of 110 dynamic routes. Routes that exceed this limit are dropped.
When using BGP to connect to a VPC, assign a unique Autonomous System Number (ASN) to the Alibaba Cloud side. This ASN must differ from the ASN assigned to vSwitches on the cloud platform.