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NE40E-M2 V800R010C10SPC500 Feature Description - LAN Access and MAN Access 01

This is NE40E-M2 V800R010C10SPC500 Feature Description - LAN Access and MAN Access
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Using Three-Segment VXLAN to Implement Layer 3 interconnection between DCs

Using Three-Segment VXLAN to Implement Layer 3 interconnection between DCs

Background

To meet the requirements of geographical redundancy, inter-regional operations, and user access, an increasing number of enterprises are deploying data centers (DCs) across multiple regions.Data Center Interconnect (DCI) is a solution that enables intercommunication between the VMs of multiple DCs. Using technologies such as VXLAN and BGP EVPN, DCI securely and reliably transmits DC packets over carrier networks. With DCI, Layer 3 intercommunication between the VMs on different subnets of multiple DCs can be implemented.

Benefits

This solution offers the following benefits to users:

  • Implements Layer 3 interworking between hosts in different DCs.
  • The routing protocols running in different DCs are independent. DCs are not required to use the same protocols.
  • It is not necessary to orchestrate information between DCs.

Principles

Three-segment VXLAN establishes one VXLAN tunnel segment in each of the two DCs and also establishes one VXLAN tunnel segment between the DCs. As shown in Figure 15-42, BGP EVPN is used to create VXLAN tunnels in distributed gateway mode within both DC A and DC B so that the VMs deployed in each DC can communicate with each other. Leaf 2 and Leaf 3 are the edge devices within the DCs that connect to the backbone network. BGP EVPN is used to configure VXLAN tunnels on Leaf 2 and Leaf 3 so that the VXLAN packets received by one DC can be decapsulated, re-encapsulated, and sent to the peer DC. This process provides end-to-end bearing for inter-DC VXLAN packets and ensures that VMs in different DCs can communicate with each other.

NOTE:

In three-segment VXLAN, only VXLAN tunnels in distributed gateway mode can be deployed within DCs.

Figure 15-42 Using three-segment VXLAN to implement DCI

Control Plane

The following describes how three-segment VXLAN tunnels are established.

NOTE:

The process of advertising routes on Leaf 1 and Leaf 4 is not described in this section. For details, see VXLAN Tunnel Establishment.

  1. Leaf 4 learns the IP address of VMb2 in DC B and saves it to the routing table for the L3VPN instance. Leaf 4 then sends a BGP EVPN route to Leaf 3.
  2. As shown in Figure 15-43, Leaf 3 receives the BGP EVPN route and obtains the host IP route contained in it. Leaf 3 then establishes a VXLAN tunnel to Leaf 4 according to the process described in VXLAN Tunnel Establishment. It sets the next hop of the route to the VTEP address of Leaf 3, re-encapsulates the route with the Layer 3 VNI of the L3VPN instance, and sets its source MAC address to the MAC address of Leaf 3. Finally, Leaf 4 sends the re-encapsulated BGP EVPN route to Leaf 2.
    Figure 15-43 Control plane

  3. Leaf 2 receives the BGP EVPN route and obtains the host IP route contained in it. Leaf 2 then establishes a VXLAN tunnel to Leaf 3 according to the process described in VXLAN Tunnel Establishment. It sets the next hop of the route to the VTEP address of Leaf 2, re-encapsulates the route with the Layer 3 VNI of the L3VPN instance, and sets its source MAC address to the MAC address of Leaf 2. Finally, Leaf 2 sends the re-encapsulated BGP EVPN route to Leaf 1.
  4. Leaf 1 receives the BGP EVPN route and establishes a VXLAN tunnel to Leaf 2 according to the process described in VXLAN Tunnel Establishment.

Data Packet Forwarding

NOTE:

A general overview of the packet forwarding process on Leaf 1 and Leaf 4 is provided as follows. For additional information, see Intra-Subnet Packet Forwarding.

  1. Leaf 1 receives Layer 2 packets destined for VMb2 from VMa1 and determines that the destination MAC addresses in these packets are all gateway interface MAC addresses. Leaf 1 terminates the Layer 2 packets and finds the L3VPN instance corresponding to the BDIF interface through which VMa1 accessed the bridge domain. Leaf 1 then searches the L3VPN instance routing table for the VMb2 host route, encapsulates the received packets as VXLAN packets, and sends them to Leaf 2 over the VXLAN tunnel.
  2. As shown in Figure 15-44, Leaf 2 receives and parses these VXLAN packets. Leaf 2 finds the L3VPN instance corresponding to the Layer 3 VNI of the packets and then searches the L3VPN instance routing table for the VMb2 host route. Leaf 2 re-encapsulates these VXLAN packets, setting the Layer 3 VNI to that carried in the VMb2 host route sent by Leaf 3 and the external destination MAC address to the MAC address carried in the VMb2 host route sent by Leaf 3. Finally, Leaf 2 sends these packets to Leaf 3.
    Figure 15-44 Data packet forwarding

  3. As shown in Figure 15-44, Leaf 3 receives and parses these VXLAN packets. Leaf 3 finds the L3VPN instance corresponding to the Layer 3 VNI of the packets and then searches the L3VPN instance routing table for the VMb2 host route. Leaf 3 re-encapsulates these VXLAN packets, setting the Layer 3 VNI and the external destination MAC address to the Layer 3 VNI and MAC address carried in the VMb2 host route sent by Leaf 4. Finally, Leaf 3 sends these packets to Leaf 4.
  4. Leaf 4 receives and parses these VXLAN packets. Leaf 4 finds the L3VPN instance corresponding to the Layer 3 VNI of the packets and then searches the L3VPN instance routing table for the VMb2 host route. Using this routing information, it forwards the packets to VMb2.
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Updated: 2019-01-02

Document ID: EDOC1100058405

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