Dark Fiber and Cisco OTV - Basic Approach and connectivity
Today I am going to discuss on the connectivity of the two datacenter and in the Active-Active state or you can called them as Connecting Multiple Active Datacenter with OTV and Dark Fiber.
First let's talk about the technologies, Cisco OTV is a Overlay Transport Virtualization technology and is used to extend the LAN segments across the datacenter or in other words you can say that extending the Layer 2 traffic over the Layer 3 network.
Note : Cisco OTV supports on Cisco Nexus 7K series switches and is not supported in Cisco Nexus 9K Switches.
Cisco OTV- Overlay Transport Virtualization technology
As I said, that Cisco OTV is the way to extend your layer 2 network across the datacenter via the Layer 3 links. OTV actually works on the MAC routing concept.
MAC and Routing ..What :)
Yes, control plane protocol in Cisco OTV is used to exchange MAC reachability information between network devices providing LAN extension functionality. This is a huge change from Layer 2 switching that traditionally leverages data plane learning, and it is justified by the need to limit flooding of Layer 2 traffic across the transport infrastructure.
Layer 2 communications between sites resembles routing more than switching. If the destination MAC address information is unknown, then traffic is dropped (not flooded), preventing waste of precious bandwidth across the WAN.
Other major features like OTV provides a native built-in multi-homing capability with automatic detection, critical to increasing high availability of the overall solution. You can use two or more devices can be used in each data center to provide LAN extension functionality without risk of creating an end-to-end loop that would actually provide you the overall stability of the design. This is achieved by using the same control plane protocol which used for the exchange of MAC address information, without the need of extending the Spanning-Tree Protocol (STP) across the overlay.
The implementation on the Nexus 7000 enforces the separation between SVI routing and OTV encapsulation for a given VLAN. This is an important consideration for the scenario depicted above, since the Nexus 7000 aggregation switches would actually have to perform both functionalities.
This separation can be achieved with the traditional workaround of having two separate network devices to perform these two functions. However, a cleaner and less intrusive solution is proposed here by introducing the use of Virtual Device Contexts (VDCs) available with Nexus 7000 platforms. Two VDCs would be deployed: an OTV VDC dedicated to perform the OTV functionalities and a Routing VDC used to provide SVI routing support.
Nexus 9K Switches are not supporting Cisco OTV features to extend your Layer 2 traffic across the datacenter. Cisco Nexus 9K Spine and Leaf switches are meant of ACI infrastructure where we are extending the Layer 2 traffic via LISP control plane and the data plane is on VXLAN.
If you have a requirement in your design to extend or create a Multi-Pod environment, I will come up with the full solution and the use cases why where we can have multi-pod environment in Datacenters ACI fabric infrastructure.
Dark Fiber
Dark fiber is a interesting word to hear when comes in-front of us and I knew that this term used for unused fiber optic cables, and in new era it becomes increasingly common to lay more fiber lines than currently needed for future use. Lets take a dip of the past when only large organizations could take the dark fiber route, but now with the new demands and the affordability of the smaller companies they are also taking these services.
Just take a fiber-based service from a carrier that is available in your region and buy/rent dark fiber to create your own wide-area network. Each option has some pros and cons when comparing performance, cost and installation time, and cost is not always the top criteria. The wait time for service availability can often be a top factor. It can sometimes be weeks or even months, depending upon the application, before a provider can complete an installation. This can be a good option for those planning ahead, but if the need is more immediate. So you can extend your Layer 2 traffic across the datacenter via Dark Fiber dedicated links and high availability and reliability. Lets have a look on a sample design where two datacenter are connected via using the dark fiber services.
First let's talk about the technologies, Cisco OTV is a Overlay Transport Virtualization technology and is used to extend the LAN segments across the datacenter or in other words you can say that extending the Layer 2 traffic over the Layer 3 network.
Note : Cisco OTV supports on Cisco Nexus 7K series switches and is not supported in Cisco Nexus 9K Switches.
Cisco OTV- Overlay Transport Virtualization technology
As I said, that Cisco OTV is the way to extend your layer 2 network across the datacenter via the Layer 3 links. OTV actually works on the MAC routing concept.
MAC and Routing ..What :)
Yes, control plane protocol in Cisco OTV is used to exchange MAC reachability information between network devices providing LAN extension functionality. This is a huge change from Layer 2 switching that traditionally leverages data plane learning, and it is justified by the need to limit flooding of Layer 2 traffic across the transport infrastructure.
Layer 2 communications between sites resembles routing more than switching. If the destination MAC address information is unknown, then traffic is dropped (not flooded), preventing waste of precious bandwidth across the WAN.
Other major features like OTV provides a native built-in multi-homing capability with automatic detection, critical to increasing high availability of the overall solution. You can use two or more devices can be used in each data center to provide LAN extension functionality without risk of creating an end-to-end loop that would actually provide you the overall stability of the design. This is achieved by using the same control plane protocol which used for the exchange of MAC address information, without the need of extending the Spanning-Tree Protocol (STP) across the overlay.
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| Fig 1.1- Sample Design for connecting the DCI via OTV |
The implementation on the Nexus 7000 enforces the separation between SVI routing and OTV encapsulation for a given VLAN. This is an important consideration for the scenario depicted above, since the Nexus 7000 aggregation switches would actually have to perform both functionalities.
This separation can be achieved with the traditional workaround of having two separate network devices to perform these two functions. However, a cleaner and less intrusive solution is proposed here by introducing the use of Virtual Device Contexts (VDCs) available with Nexus 7000 platforms. Two VDCs would be deployed: an OTV VDC dedicated to perform the OTV functionalities and a Routing VDC used to provide SVI routing support.
Nexus 9K Switches are not supporting Cisco OTV features to extend your Layer 2 traffic across the datacenter. Cisco Nexus 9K Spine and Leaf switches are meant of ACI infrastructure where we are extending the Layer 2 traffic via LISP control plane and the data plane is on VXLAN.
If you have a requirement in your design to extend or create a Multi-Pod environment, I will come up with the full solution and the use cases why where we can have multi-pod environment in Datacenters ACI fabric infrastructure.
Dark Fiber
Dark fiber is a interesting word to hear when comes in-front of us and I knew that this term used for unused fiber optic cables, and in new era it becomes increasingly common to lay more fiber lines than currently needed for future use. Lets take a dip of the past when only large organizations could take the dark fiber route, but now with the new demands and the affordability of the smaller companies they are also taking these services.
Just take a fiber-based service from a carrier that is available in your region and buy/rent dark fiber to create your own wide-area network. Each option has some pros and cons when comparing performance, cost and installation time, and cost is not always the top criteria. The wait time for service availability can often be a top factor. It can sometimes be weeks or even months, depending upon the application, before a provider can complete an installation. This can be a good option for those planning ahead, but if the need is more immediate. So you can extend your Layer 2 traffic across the datacenter via Dark Fiber dedicated links and high availability and reliability. Lets have a look on a sample design where two datacenter are connected via using the dark fiber services.
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| Fig 1.2- Datacenter Connectivity via Dark Fiber |
Today, with the traditional Ethernet service you tends to be both more scalable and lower cost than SDH/SONET. But bandwidth options are 100 Mbps Fast Ethernet, 250 Mbps, 500 Mbps, 1 Gbps Gigabit Ethernet and 10GbE.
Changing time and the demands of the high bandwidth requirements like 100 Gb-Ethernet services and 100 GbE can now be ordered in some areas, this high level of bandwidth remains expensive compared to dark fiber solutions. When an organization’s demand is more like 10 gigabits, they need alternatives.
This article is just a introduction to both the technologies while i will come up with the next article where i will explain the OTV with features and use cases and then Dark-Fiber as well.
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