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Community Member

Dlci and frame relay


hope someone could explain me something -

as i understand the dlci is a uniqe number which identify a uniqe point to every

network. ( its symbolize the first point where the network is connected to the f/r cloud , or the uniqe dce of every network ) [correct me if i wrong]

and in this way the pvc could be created - it connects two uniqe dlci .

anyway, how can it be that in my company for example, all the routers which

connect to us using the same dlci. yes in the center router there is a uniqe dlci

to each router that connect to it.

but yet - i can't understand how can it be that many router in the same f/r cloud

can have the same dlci.

when my router want to create a pvc connection, it search for dlci number 19

how it know to which dlci number 19 to connect ???


thanks u for your answers


Re: Dlci and frame relay


the answer is very simple. The dlci 19 in your case has only local significance. As you know if there are two routers in a frame-relay cloud and a pvc exist between them, then each end of the pvc (each router ) should be having a unique dlci.

In your case the central site is like a hub and the remote sites are like spokes. There for pvcs exists only from spoke to hub. In your case, there is no pvc existing from one spoke to another. So all the remote sites can use the same dlci number. For every remote site (say N, where N is any number), there will be N pvcs, each pvc from hub to the spoke, and the hub will have a unique dlci number for each pvc. While the spokes can use the same dlci number, as the pvc exists only from spoke to hub

Consider this example....

1 hub site and 3 remote sites.

we need 3 pvcs for a hub and spoke topology.

at the hub, we configure 3 dlcis say 100, 200, 300. At each of the remote sites we configure the dlci number 400 (all the 3 sites use the same dlci).

Now, the 3 pvcs are defined as follows. 100 - 400, 200-400 and 300-400.

Eventhough all 3 sites uses the same dlci number, they all belong to different pvcs. Also you should note that, routing protocols help in communication between one spoke to another spoke. Communication between spokes, happen only through the hub site.

Hope thats clear now!

Community Member

Re: Dlci and frame relay

thanks you for your explanation .

i think i understood it .

just one more little thing -

what is the meaning of the word "spoke" ?

thanks again

Re: Dlci and frame relay


Its just an analogy used to explain the particular frame-relay topology.

Assume a central site and 10 remote sites. Each remote site has one pvc to the central site.

So if you draw a diagram of the topology, with the central site at the centre and the remote sites around it, there would be one line drawn from each remote site to the central site, indicating each pvc. This would look like the wheel of a bicycle with hub cap at the center and spokes going outwards from the hub.

In the example, the central site is denoted as "HUB" and the remote site is denoted as "SPOKE".

Hope that analogy is clear.

Community Member

Re: Dlci and frame relay

thank u very much

you are the best

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