VMM Interconnection Design

The logical network of a DC serves VMs, and associates compute and network resources through the SDN controller. In the cloud DCN solution, the SDN controller can interconnect with multiple VMMs, including OpenStack and vCenter. In the multi-site solution, one site is a fabric network and is managed by one SDN controller. One SDN controller can connect to multiple VMMs, and each VMM manages only the VMs and connects only to the SDN controller at the local site. For details, see Figure 7.15.

Deployment Solution Design

The preceding describes the conceptual model and service model of the multi-site scenario. The following section describes how Layer 2 and Layer 3 communication between fabric networks is implemented.

In Figure 7.16, DC1 and DC2 are deployed independently, and each DC is configured with an independent network resource pool. If the two DCs need to communicate with each other at Layer 3, Layer 3 DCI can be deployed.

FIGURE 7.15 VMM interconnection design.

In each DC, standard spine-leaf networking is used and a fabric gateway needs to be configured for DCI.

Three solutions are available to implement DCI physical network interconnection:

• • Solution 1: For a campus with multiple sites, interconnection can be implemented through core switches.
• • Solution 2: In a scenario where a small number of sites are deployed and DC fabric gateways are directly connected, direct interconnection through bare optical fibers or DWDM is applicable.
• • Solution 3: In a scenario with many remote sites, WAN interconnection is applicable. It is recommended that the DCI logical network interconnection be implemented using three-segment VXLAN. Alternatively, it can be implemented through Layer 3 routing (an IGP or BGP). The VXLAN solution is not affected by customer’s network planning and is applicable on a large scale.

Three-segment VXLAN is recommended for Layer 2 and Layer 3 communication between DCs. BGP EVPN is configured on a DCI gateway to create a VXLAN tunnel. VXLAN packets received from one DC are decapsulated, re-encapsulated, and then sent to the other DC. This mode ensures that end-to-end VXLAN packets are successfully transmitted across DCs and VMs in different DCs communicate with each other.

An IGP or BGP is deployed between DCI devices, which function as VTEPs on fabric networks. The IGP or BGP is used to ensure connectivity of service network segments between fabric networks. Based on IGP or BGP routes, the DCI devices directly decapsulate VXLAN packets and forward the packets. This mode, however, requires strict IP address planning. That is, routes corresponding to IP addresses in all DCs must be reachable on the Internet. This mode is applicable to interconnection between multiple DCs in an enterprise and places stringent requirements on the overall plan.