3.3.2. Peering Configuration

ExpressRoute circuits support two peering types:

Private Peering:

• Connects to VNets (IaaS/PaaS with private endpoints)
• Uses private IP addresses (RFC 1918)
• BGP session between your router and MSEE
• Most common peering type

Microsoft Peering:

• Connects to Microsoft 365, Dynamics 365, Azure PaaS public endpoints
• Uses public IP addresses you own (or NAT)
• Requires route filters to select services
• Less common—Private Endpoints often preferred for PaaS

BGP Session Establishment:

Route Filters (Microsoft Peering only):

• Select which Microsoft services to advertise
• Options: Azure Public (all regions), specific regions, or specific services
• Reduces routing table size

BGP Communities: Microsoft tags routes with BGP communities indicating the Azure region. Use these to prefer certain paths or filter routes.

⚠️ Exam Trap: Private peering connects to VNets; Microsoft peering connects to Microsoft public services. Don't confuse them—a question about "accessing Azure SQL via ExpressRoute" likely involves private peering with a Private Endpoint, not Microsoft peering.