Configuring the NFVI Distributed Gateway Function (BGP EVPN over E2E SR Tunnels)

In the NFVI telco cloud solution, the NFVI distributed gateway function allows mobile phone traffic to be processed by vUGWs and vMSEs and transmitted over a DCN through E2E SR tunnels as well as being transmitted within a DCN in load balancing mode.

Usage Scenario

The NFVI telco cloud solution uses the DCI+DCN networking. A large amount of mobile phone traffic is sent to vUGWs and vMSEs on the DCN. After being processed by the vUGWs and vMSEs, the mobile phone traffic is forwarded over the DCN to destination devices on the Internet. The destination devices send traffic to mobile phones in similar ways. To achieve these functions and ensure traffic load balancing on the DCN, you need to deploy the NFVI distributed gateway function.

Figure 1 shows the networking of an NFVI distributed gateway (BGP EVPN over E2E SR tunnels). DC-GWs, which are the border gateways of the DCN, exchange Internet routes with external devices over PEs. L2GW/L3GW1 and L2GW/L3GW2 are connected to VNFs. VNF1 and VNF2 that function as virtualized NEs are deployed to implement the vUGW functions and vMSE functions, respectively. VNF1 and VNF2 are each connected to L2GW/L3GW1 and L2GW/L3GW2 through IPUs.

In NFVI distributed gateway networking (BGP EVPN over E2E SR tunnels), the number of BDs needs to be planned based on the number of network segments corresponding to each IPU. An example assumes that the four IP addresses planned for four IPUs belong to four network segments. In this case, four BDs need to be planned. You need to configure the BDs and the corresponding VBDIF interfaces on all L2GW/L3GWs and bind all the VBDIF interfaces to the same L3VPN instance. In addition, the following functions need to be deployed on the DCN:

Establish BGP VPN peer relationships between VNFs and DC-GWs so that the VNFs can advertise mobile phone routes (UE IP) to DC-GWs.
On L2GW/L3GW1 and L2GW/L3GW2, configure static VPN routes with the IP addresses of VNFs as the destination addresses and the IP addresses of IPUs as next-hop addresses.
Deploy EVPN RRs which can be either a standalone device or a DC-GW. In this section, BGP EVPN peer relationships are established between all L2GW/L3GWs, PEs, and DC-GWs, DC-GWs are deployed as RRs to reflect EVPN routes, and other devices function as RR clients. The functions of a BGP EVPN RR are as follows:
- DC-GWs can reflect the mobile phone routes learned by VNFs to L2GW/L3GWs and PEs so that mobile phone routes can be transmitted outside the DCN and the traffic sent to mobile phone users can be introduced to the DCN. Route-policies need to be configured DC-GWs so that the mobile phone routes sent by DC-GWs to L2GW/L3GWs and PEs carry the gateway addresses which are VNFs' loopback addresses.
- DC-GWs receive the IP prefix routes destined for VNFs from an L2GW/L3GW based on BGP EVPN peer relationships and reflect the IP prefix routes to PEs and other L2GWs/L3GWs. The EVPN RR can also be used to synchronize the MAC or ARP routes of IPUs and the IP prefix routes destined for VNFs between L2GW/L3GWs.
Configure static default routes on PEs and use the EVPN RRs to reflect the static default routes to L2GW/L3GWs.
Deploy SR tunnels between PEs and L2GW/L3GWs and between DC-GWs and L2GW/L3GWs to carry service traffic.
The traffic transmitted between mobile phones and the Internet over VNFs is north-south traffic. The traffic transmitted between VNF1 and VNF2 is east-west traffic. To achieve load balancing of east-west traffic and north-south traffic, deploy the load balancing function on DC-GWs and L2GW/L3GWs.

The NFVI distributed gateway function supports both IPv4 and IPv6 services. If a step does not differentiate IPv4 and IPv6 services, this step applies to both IPv4 and IPv6 services.

Figure 1 NFVI distributed gateway networking

Pre-configuration Tasks

Before configuring the NFVI distributed gateway function, complete the following tasks:

Allow the routes between PEs and DC-GWs and between DC-GWs and L2GW/L3GWs to be reachable.
Deploy SR tunnels between PEs and L2GW/L3GWs and between DC-GWs and L2GW/L3GWs.
Configure the BD EVPN function on DC-GWs and L2GW/L3GWs. The configuration includes creating EVPN instances and L3VPN instances, establishing BGP EVPN peer relationships, and configuring VBDIF interfaces. On DC-GWs, the configuration involves only creating L3VPN instances and establishing BGP EVPN peer relationships.
Configure the static routes destined for VNF1 and VNF2 on L2GW/L3GWs by referring to Static VPN IPv4 Routes or Static VPN IPv6 Routes.

Configuring Route Recursion over SR Tunnels: By default, routes are recursed to a BD EVPN or BGP VPNv4/VPNv6 network over MPLS LDP tunnels. If SR tunnels are used to carry service traffic, the function to recurse routes over SR tunnels must be configured.

Configuring Route Advertisement on PEs: The route advertisement function allows PEs to advertise default static routes to L2GW/L3GWs through BGP EVPN RRs.

Configuring Route Advertisement on DC-GWs: Route advertisement can be configured on DC-GWs to allow the DC-GWs to construct their own forwarding entries based on the received EVPN routes.

Configuring Route Advertisement on L2GW/L3GWs: Route advertisement can be configured on L2GW/L3GWs to allow the L2GW/L3GWs to construct their own forwarding entries based on the received EVPN or BGP routes.

Configuring the Load Balancing Function: The load balancing function needs to be deployed to achieve balanced loads of network traffic.

Verifying the Configurations of the NFVI DistributedGateway Function: After configuring the NFVI distributed gateway function, verify the configurations. On DC-GWs, you can view the VPN peer relationships between DC-GWs and VNFs and the information about the mobile phone routes received from VNFs.