Arista Network datacenter design: Implementing VXLAN Routing

Today I am talking about the VXLAN protocol routing. VXLAN routing is enabled by creating a VLAN interface (SVI) on a VLAN that is associated to a VNI. As you know that VXLAN is called as Virtual extensible LAN. VXLAN is a way to extend the Layer 2 subnets over layer 3 network. VXLAN is now one of the demanding way of extended the Layer 2 traffic. 

Earlier we have so many technologies to do so like we have VPLS, MPLS and OTV( Cisco) in the Datacenter network. But VXLAN is used for the fabric network where you can have end to end tunnels within your LAN network. 

Now a days if you are looking the enterprise network you will find that VXLAN is used in the Datacenter and Campus networks with the Software defined. VXLAN is implemented in the datacenter where Spine-Leaf architecture is followed. Below is the basic Arista Spine-Leaf architecture for reference only.

Fig 1,1- Arista Datacenter -MLAG


Let's talk about the VXLAN implementation routing on Arista devices. We have two switches connected via core routers and end devices are connected to that switches. In the case of VXLAN you should aware about the three things and these things are

  1. VLAN : Virtual LAN and i guess everybody knows about it
  2. VNI: Virtual Network Identifier, VXLAN network identified by a unique VNI is an isolated logical network and a 24 bit number that gets added to the VXLAN frame which allows a theoretical limit of 16 million separate networks
  3. VTEP: VXLAN Tunnel End Point, So VTEP is the end point that is responsible for encapsulating the L2 Ethernet frame in a VXLAN header and forward that on to the transport network as well as the reversal of that process
Fig 1.2- VXLAN Connectivity and VTEP


Assigning an IP address to the VTEP
NDNA(config)#interface vxlan 1 
NDNA(config-if-Vx1)#
NDNA(config)#interface loopback 15 
NDNA(config-if-Lo15)#ip address 10.25.25.3/24 
NDNA(config-if-Lo15)#exitttlbits(config)#interface vxlan 1 
NDNA(config-if-Vx1)#vxlan source-interface loopback 15 
NDNA(config)#interface vxlan 1 
NDNA(config-if-Vx1)#vxlan udp-port 5500 

Assigning VNI to a VLAN
NDNA(config)#interface vxlan 1 
NDNA(config-if-Vx1)#vxlan vlan 100 vni 100 
NDNA(config-if-Vx1)#vxlan vlan 200 vni 10.10.200 
NDNA(config-if-Vx1)#vxlan vni notation dotted 

Assigning a Multicast Group to the VTI 
NDNA(config)#interface vxlan 1 
NDNA(config-if-Vx1)#vxlan multicast-group 227.10.1.1 

VXLAN head-end replication flood list 
NDNA(config)#interface vxlan 1 
NDNA(config-if-Vx1)#vxlan flood vtep 10.1.1.1 10.1.1.2 
NDNA(config-if-Vx1)#vxlan vlan 101-102 flood vtep 11.1.1.1 11.1.1.2 11.1.1.3 

Above are the basic configuration to start with the VXLAN configuration. Now lets discuss about the implementation of the VXLAN routing.

VXLAN routing is enabled on Switch A by configuring a VLAN interface with an IP address of 10.10.10.1. Packets from Devices A-1 and B-2 that have destinations other than 10.10.10.0/28 are VXLAN-bridged to the default gateway (10.10.10.1), then routed from Switch A.