What is cisco mac address free#

Hence, clarifies the term MAC-in-MAC routing. It is quite evident from the header that the outer MAC is FabricPath header and the inner MAC is Classical Ethernet header.

The ODA is used for known Unicast whereas the FTag is used for unknown Unicast, Multicast and Broadcast.

FTag (Forwarding Tag): Used for traffic forwarding in the FabricPath domain.

Switch ID: Used for source and destination switches.

It is also responsible for load-balancing traffic using ECMP. It helps to have the same view of topology throughout the FabricPath network.

It doesn’t require any configuration, you only need to enable FabricPath and the IS-IS runs automatically in the background. Layer 2 IS-IS is different from Layer 3 IS-IS. It offers ECMP and loop prevention by using TTLįabricPath uses ISIS so as to learn the shortest path to each Switch ID based on link metrics/path cost, upto 16 equal (ECMP) routes can be installed.Of the MAC addresses based on active flows FabricPath works by the principle of Conversational MAC learning.Each switch is going to have its own Layer 2 topology with the help of Dijkstra SPF calculation. Provides design flexibility, redundancy and fault tolerance.Maximizes bandwidth availability using ECMP.It is a 12-bit identifier and is used frequently in the Fabricpath header. IMPORTANT: Each device in a FabricPath domain has a Switch ID that is either manually assigned or dynamically allocated via DRAP (Dynamic Resource Allocation Protocol). To understand this further, you can refer to the FabricPath header. FabricPath is simple, flexible, resilient, scalable and offers ECMP (Equal Cost Multi-pathing).įabricPath is also known as MAC-in-MAC routing or forwarding or encapsulation or tunneling because the frame is MAC-in-MAC encapsulated and routed over to the destination FabricPath switch. It is important to note that FabricPath has still Ethernet as an underlying protocol same like the Spanning Tree Protocol. So, you can have IS-IS at Layer 3 in the network too at the same time. This IS-IS is called Layer 2 IS-IS and is independent of Layer 3 IS-IS.

What is cisco mac address free#

On the other hand, STP is only plug and play and does not have any Layer 3 intelligence.įabricPath has got Layer 3 routing protocol at the background to support intelligence and that is IS-IS and it helps loop free topology. It combines both Layer 2 and Layer 3 functions, thus giving simplicity of Layer 2 and also the intelligence of Layer 3. The biggest advantage of FabricPath is that it gives us the flexibility along with loop free connectivity that STP couldn’t do and is therefore run in Data Centers as a replacement of Spanning Tree Protocol.Ĭisco FabricPath is about routing your data center traffic and helps doing load-sharing. So, in order to do active-active forwarding and build loop free topology at the same time at Layer 2, FabricPath was introduced.įabricPath is Cisco proprietary and works in the same way as TRILL that is an IETF standard. As we know that routing protocols have got the intelligence to do load-sharing, but STP not being intelligent enough can’t do active-active forwarding. It is important to note that STP does loop avoidance at Layer 2 whereas routing protocols do loop avoidance at Layer 3. It runs IS-IS in the control plane and for the same reason, it is also called Layer 2 routing.įabricPath is in fact the solution to avoid STP and hence considered as a replacement for Spanning Tree Protocol.Ĭisco FabricPath | The Solution to Avoid STP What is Cisco FabricPath? Cisco FabricPath is a technology that is designed to overcome STP limitations including scalability, convergence and unnecessary flooding.