VMware: Understanding Layer 2 Extensions for the Hybrid Cloud
Taking a VLAN and extending that broadcast domain across two sites can be identified by many names including; Data Center Interconnect (DCI), Data Center Extension (DCE), Extended Layer 2 Network, Stretched Layer 2 Network, Stretched VLAN, Extended VLAN, Stretched Deploy, Layer 2 VPN. With all these different aliases, it’s no wonder why people are confused by how any of it works, what the implications of routing different networks between sites are, or why you should consider stretching networks in first place.
Stretching a network allows VMs talk over the same broadcast domain when they exist at different physical locations, removing the need to re-architect your network topology. Additionally, this allows you to retain IP and MAC addresses when you vMotion a VM between these locations, which can be very useful from a licensing perspective for some software applications. These capabilities create the hybrid ‘feel’ of your datacenters by allowing you to grow or shrink applications at either site without having to touch the networking.
There are multiple ways to implement a stretched layer 2 network between datacenters ranging from hardware-based solutions such as Cisco’s OTV on the Nexus 7000, to options with VMware’s NSX platform like the one Tom Fojta expertly explains here. The downfall with this is you may lack control over the physical equipment your cloud provider utilizes, or not have the level of access required to leverage these options. And if you’ve found a way to stretch these networks you now need to worry about potential loops, managing flow affinity to prevent traffic drops and duplicate ARP responses.
Read the entire article here, Understanding Layer 2 Extensions for the Hybrid Cloud
via the fine folks at VMware!