I-BGP synchronization with IGP

The BGP synchronization rule requires that when a BGP router receives information about a network from an IBGP neighbor, it does not use that information until a matching route is learned via an IGP or static route.

What does it mean a matching route in this statement? Same prefix? Next-hop? Etc.

What do you mean exactly by “does not use that information”? In global routing table? Advertising the route (information) to peers?

fig. 1. Network setup

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Vlan propagation and Cisco FabricPath

PC-A and PC-B belong to the same broadcast domain that is defined by vlan X. Without FabricPath (FP), a frame that is sent by PC-A is received by FP-SW1. PC-1 MAC source address is learnt by FP-SW1 in CAM to ease further frame local forwarding decisions.

Initially PC-1 did not know PC-B MAC address and floods PC-A frame to FP-SW2 and FP-SW3. Similarly FP-SW2 and FP-SW3 learns PC-A MAC source address and flood it over all vlan ports except the one the frame was received on. Continue reading “Vlan propagation and Cisco FabricPath”

At the begining, … it was not DMVPN!

The simplest way to interconnect 3 or more routers in the same broadcast domain (and the same subnet) is by attaching them to a switch (or hub) in the same vlan.

In case they’re separated by long distances, an ISP may be required to put them together. From a network access perspective, they could be interconnected in ways such as:

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