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Dell EMC SmartFabric OS10 User Guide Release 10.5.1

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Example: VXLAN BGP EVPN — Centralized L3 gateway

The following VXLAN with BGP EVPN example uses a centralized Layer 3 gateway to perform virtual-network routing. It is based on the sample configuration in Example: VXLAN BGP EVPN — Multiple AS topology.

In the VXLAN BGP EVPN multiple AS topology, all VTEPs are configured to perform distributed L3 gateway routing, in which each VTEP routes VXLAN traffic. Routing decisions are made by ingress VTEPs.

However, in a multi-tenant network, some VTEPs may operate only in Layer 2 VXLAN mode and perform only Layer 2 functions. In this case, configure routing for Layer 2 VTEPs on one Layer 3 VTEP that supports Layer 3 VXLAN functionality. The Layer 2 VXLAN-capable VTEPs are connected with the centralized Layer 3 gateway either directly or through an IP underlay fabric. Any ingress routing traffic on a Layer 2 VTEP is switched to the Layer 3 centralized gateway. All routing decisions are made by the centralized gateway to forward VXLAN traffic to the destination Layer 2 VTEP.

The following centralized L3 gateway example for VXLAN BGP EVPN uses a Clos leaf-spine topology. In this example:
  • VTEP 1 and VTEP 2 in VLT 1 operate as a L2 gateway.
  • VTEP 3 and VTEP 4 in VLT 2 operate as a centralized L3 gateway.
  • Host A and Host B are connected to the L2 gateway. The L2 gateway is connected to a centralized L3 gateway through an IP underlay fabric.
  • You must configure the IP address and anycast IP address of the virtual networks in the centralized L3 gateway VTEP. It is not necessary to configure these addresses in the L2 gateway VTEPs.

Routing for tenant L3 traffic is not performed on the L2 VTEPs. The L2 VTEPs forward tenant traffic to the centralized L3 gateway in VLT 2. The L3 gateway routes traffic between L2 tenant segments.

Figure 1. VXLAN BGP EVPN with centralized L3 gateway. XLAN BGP EVPN with centralized L3 gateway
Centralized Layer3 Gateway Routing

VTEP 3 Leaf Switch

NOTE: This centralized L3 gateway example for VXLAN BGP EVPN uses the same configuration steps as in Example: VXLAN BGP EVPN — Multiple AS topology. Configure each spine and leaf switch as in the Multiple AS topology example, except:
  • Because VTEPs 1 and 2 operate only in Layer 2 VXLAN mode, do not configure IP switching in the overlay network. This step consists of configuring virtual network interfaces with IP addresses, anycast IP addresses, and anycast gateway MAC addresses.
  • Configure IP switching in the overlay network only on VTEPs 3 and 4.

1. Configure IP switching in the overlay network.

Create a tenant VRF.

OS10(config)# ip vrf tenant1
OS10(conf-vrf)# exit

Configure an anycast gateway MAC address.

OS10(config)# ip virtual-router mac-address 00:01:01:01:01:01

Configure routing on the virtual networks.

OS10(config)# interface virtual-network10000
OS10(conf-if-vn-10000)# ip vrf forwarding tenant1
OS10(conf-if-vn-10000)# ip address 10.1.0.233/16
OS10(conf-if-vn-10000)# ip virtual-router address 10.1.0.100
OS10(conf-if-vn-10000)# no shutdown
OS10(conf-if-vn-10000)# exit

OS10(config)# interface virtual-network20000
OS10(conf-if-vn-20000)# ip vrf forwarding tenant1
OS10(conf-if-vn-20000)# ip address 10.2.0.233/16
OS10(conf-if-vn-20000)# ip virtual-router address 10.2.0.100
OS10(conf-if-vn-20000)# no shutdown
OS10(conf-if-vn-20000)# exit

VTEP 4 Leaf Switch

1. Configure IP switching in overlay network.

Create a tenant VRF.

OS10(config)# ip vrf tenant1
OS10(conf-vrf)# exit

Configure an anycast gateway MAC address.

OS10(config)# ip virtual-router mac-address 00:01:01:01:01:01

Configure routing on the virtual networks.

OS10(config)# interface virtual-network10000
OS10(conf-if-vn-10000)# ip vrf forwarding tenant1
OS10(conf-if-vn-10000)# ip address 10.1.0.234/16
OS10(conf-if-vn-10000)# ip virtual-router address 10.1.0.100
OS10(conf-if-vn-10000)# no shutdown
OS10(conf-if-vn-10000)# exit

OS10(config)# interface virtual-network20000
OS10(conf-if-vn-20000)# ip vrf forwarding tenant1
OS10(conf-if-vn-20000)# ip address 10.2.0.234/16
OS10(conf-if-vn-20000)# ip virtual-router address 10.2.0.100
OS10(conf-if-vn-20000)# no shutdown
OS10(conf-if-vn-20000)# exit

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