Extending your subnet in Azure with VXLan

Continuing with networking in Azure, today I want to talk about how extend the subnets in Azure with VXLAN. To those who do not know VXLAN, it proposes to generate a virtual network to overlap a LAN which will work as base. VXLAN technology uses a layer 3 technology, in order to extend the network, as it shows the following diagram, where the same subnet exists on both sides (Azure and OnPrem):

Ejemplo de extensión de subred

So here the key is that you need a tunel between Azure and OnPrem in order to exchange traffic, but also take into account the following:

  • IP addresses of on-premises hosts are configured as additional IP addresses on the Network Interface Card (NIC) of the Azure VM (using Azure orchestration system);
  • IP addresses of Azure hosts are configured as additional IP addresses of the NIC of on-premises VM.

Whenever an on-premises host tries to reach an Azure VM it sends out an ARP request, and the on-premises Extended Network VM replies to it.

Whenever an Azure VM tries to reach an on-premises host, the Azure Virtual Router sends the traffic to the local IP address which is owned by the Azure VM running Extended Network code.

Take care and happy networking!