Comparing Layer-2 and Layer-3 connections for Direct Link
IBM Cloud® Direct Link accepts OSI Layer-2 and Layer-3 partner interconnections from network service providers (NSPs). Some network service providers offer services for both of these layers on different networks, however, some providers might choose not to interconnect all of their networks into IBM Cloud.
When planning your IBM Cloud Direct Link deployment, consider the characteristics that are associated with Layer-2 and Layer-3 connections, so you can create a deployment that best suits your needs.
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. This means when you order Direct Link Connect via the IBM Portal, you need to populate the Layer 3 providers 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 functionalities across their network when using Layer-3 connections, such as ASN prepend, GRE tunneling, and so forth. Be sure to check with your provider about possible restrictions.
Partner interconnection table
The following table summarizes the type of connections that each IBM Cloud partner provides.
| Partners | Interconnection type |
|---|---|
| Bell Canada | Layer 3 |
| British Telecom | Layer 3 |
| CenturyLink IP VPN | Layer 3 |
| CenturyLink Dynamic Connections | Layer 2 |
| Chief Telecomm | Layer 2 |
| China Unicom | Layer 3 |
| Colt | Layer 2 |
| Console Connect | Layer 2 |
| Epsilon | Layer 2 |
| EU Networks | Layer 2 |
| IBM BlueFringe | Layer 3 |
| Intercloud | Layer 3 |
| IXReach | Layer 2 |
| Neutrona | Layer 2 |
| nextGen GNPP | Layer 3 |
| NTT | Layer 3 |
| Orange Business Services | Layer 3 |
| PacketFabric | Layer 2 |
| Softbank | Layer 3 |
| SES Networks | Layer 2 |
| Tata IZO™ Private Connect | Layer 3 |
| Arelion | Layer 3 |
| Tokai | Layer 2 |
| Vodafone | Layer 3 |
| Zayo Cloud Link | Layer 2 |