Considerations for Layer-2 connections

For each VLAN-based virtual circuit, which you create with a Layer-2 partner interconnection, you must configure and establish a BGP session between your on-premises routers and the IBM Cloud XCR. IBM Cloud provides you with a /31 IPv4 assignment to establish a BGP session with your router.

• Layer-2 networks offer options for simple one-to-one connections between enterprises and IBM Cloud.
• Layer-2 services rely on VLANs instead of IP addresses.
• Layer-2 services might be lower cost and lower latency, and they might consume less overhead than Layer-3 services.
• Layer-2 networks do not impose restrictions on the Layer-3 features that an enterprise can enable.

Considerations for Layer-3 connections

For Layer-3 connections, for each virtual circuit, your service provider establishes a BGP session between IBM Cloud XCRs and the provider's edge routers. You do not need to configure BGP with IBM Cloud for your on-premises router because your service provider manages the BGP configuration to IBM Cloud.

When you order Direct Link Connect through the IBM Cloud console, you need to populate the Layer-3 provider's ASN for the BGP session, not your customer ASN.

• Layer-3 IP VPN or AVPN networks enable "any-to-any" connectivity.
• Layer-3 networks require the network service provider to maintain a BGP session between the enterprise and IBM Cloud.
• Certain network service providers might restrict certain functions across their network when you use Layer-3 connections, such as ASN prepends, GRE tunneling. Be sure to check with your provider about possible restrictions.

Provider interconnection table

The following table summarizes the type of connections that each IBM Cloud partner provides.