Approach to Cisco OTV- Overlay Transport Virtualization in Datacenter DCI connectivity
Today I am
going to talk about the one of the overlay protocol used in the traditional
Cisco data center environment. This Overlay protocol is widely used where you
are going to connect two different data center across the globe having core
Cisco switching. The Overlay protocol which we are talking about it Cisco OTV.
OTV stands for Overlay Transport Virtualization.
What is Cisco OTV- Overlay Transport
Virtualization ?
Cisco OTV is
an overlay protocol and used to simplifies extending Layer 2 applications
across distributed data centers. We can implement Data Center Interconnect
(DCI) between sites without altering or re-configuring your existing network
design.
With OTV
you can install virtual computing assets and clusters throughout physically spread
data centers across the globe. OTV can provide you Transparent workload
mobility, Business Resiliency and computing resources efficiency.
What king of traffic can be transmitted over
Cisco OTV ?
OTV is an
IP-based functionality that has been intended to deliver Layer 2 extension abilities
over any transport structure Layer 2 based, Layer 3 based, IP switched, label
switched. OTV offers an overlay that permits Layer 2 connectivity among independent
Layer 2 domains while maintaining these domains autonomous and protective the
fault-isolation, resiliency, and load-balancing profits of an IP-based
interconnection.
Fig 1.1- Basic OTV connectivity between sites |
Cisco OTV initiates the idea of MAC routing which capitals a control plane protocol is used to interchange MAC reachability data between network devices offering LAN extension capabilities. This is a important shift from Layer 2 switching that conventionally influences data plane learning, and it is acceptable by the requirement to threshold overflowing of Layer 2 traffic throughout the transport structure.
Cisco OTV also presents the impression of dynamic encapsulation for Layer 2 traffic that essential to be directed to faraway sites. Each Ethernet frame is separately encapsulated into an IP packet and transported throughout the transport network. This abolishes the requirement to inaugurate virtual circuits, called Pseudo wires, among the data center localities.
What are the components of the OTV overlay protocol ?
We have various components in the OTV overlay protocol and these components are
OTV Edge device
OTV internal interfaces
OTV Join interface
OTV Overlay Interface
What is OTV Edge device ?
The Cisco
OTV edge device collects Layer 2 traffic for all VLANs that required to be
extended to faraway sites and dynamically encapsulates the Ethernet frames into
IP packets that are then sent across the transport infrastructure. In a traditional
architecture of Cisco OTV, Cisco Nexus core 7000/7700 will be your OTV edge
device but with the different VDC.
Can you explain the interfaces used in the Cisco
OTV which are mentioned above ?
OTV internal Interface: To accomplish OTV functionality,
the edge device must accept the Layer 2 traffic for all VLANs that required to
be extended to far branch sites. The internal interfaces collects the layer 2 traffic
from the core switch and configured as access or trunk interface. It do the
basic functions of local switching, STP, Data plane learning and flooding
OTV Join Interface: As you might know that the
connectivity between one data center to another is with the layer 3 IP domain
and the traffic we collected from the Core switches is Layer 2 traffic which we
have it on the OTV internal interface, now this traffic encapsulated and send
it to the layer 3 domain of the data center. So OTV join interface will work as
a source port for sending the traffic across the other sites.
It can also
perform to discover the edge devices on the remote sites. It also form OTV
adjacency with the other OTV edge devices belonging to the same VPN. It can
also use for Send/receive MAC reachability information and Send/receive unicast
and multicast traffic.
OTV Overlay Interface: This is the logical interface by
which the traffic flows. It is a multi-access and multicast-capable interface
that must be clearly described by the client and the complete OTV configuration
is applied.
Every time
the OTV edge device accepts a Layer 2 frame destined for a far ended data
center site, the frame is logically dispatched to the Overlay interface. This initiates
the edge device to accomplish the dynamic OTV encapsulation on the Layer 2
packet and direct it to the Join interface toward the routed domain.
Can you give some idea over the Cisco OTV
Neighbor Discovery ?
Every OTV
edge appliance transmit an IGMP information to join the exact ASM group used to
bring control protocol exchanges. The edge devices join the group as hosts,
leveraging the Join interface. This occurs without permitting PIM on this
interface. The only obligation is to identify the ASM group to be used and
associate it with a given Overlay interface.
Fig 1.3- OTV between Data centers |
The OTV
control protocol running on the one OTV edge appliance produces Hello packets
that required to be directed to all other OTV edge devices. This is mandatory
to interconnect its existence and to activate the formation of control plane
adjacency.
The OTV
Hello messages required to be directed throughout the logical overlay to spread
all OTV remote appliances. For this to occur, the frames must be
OTV-encapsulated, enhancing an exterior IP header. The source IP address in the
exterior header is set to the IP address of the Join interface of the edge
device, while the destination is the multicast address of the ASM group
dedicated to transmit the control protocol. The follow-on multicast frame is
then directed to the Join interface to the Layer 3 network domain.
Fig 1.4- Basic OTV Configuration |
The
multicast frames are transmitted through the transport and simulated to extend
all the OTV edge appliances that tied that multicast group G. The accepting OTV
edge devices decapsulate the packets. The Hellos are accepted to the control
protocol process.