convention for frame relay diagrams - cross posted from


I've done the CCNA and am working on the CCNP bcran exam and I've got one major issue that steadfastly refuses to go away! When looking at diagrams of a frame relay network there appears to be no consistency in where the DLCI is drawn on the diagram. Sometimes the DLCI written above a link seems to mean the local dlci, whereas at other times it's the other ends DLCI.

For example

frame-relay map ip 200 broadcast cisco

Sometimes has a diagram with the 200 drawn next to the router, at other times the 200 is on the other side.

This is an issue that I've have for months and I'm getting nowhere. Am I just stupid or is there no set convention?

Yours confused.


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John Smith
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You will be well aware that a DLCI is local to an interface.


Site A - DLCI 16 --FR Cloud -- DLCI 16 Site B Site A - DLCI 17 --FR Cloud -- DLCI 16 Site C

Site A uses 16 to reach Site B Site B uses 16 to reach Site A Site A uses 17 to reach Site C Site C uses 16 to reach Site A

The above is a standard addressing scheme and you would see the DLCI's on the outgoing link on the diagram.

There is another concept used to simplify understanding the destination of PVC's called global addressing. This is just a conceptual addressing and does not make frame-relay addressing work any different. It just means the DLCI's are picked intelligently and not just sequentially.

For this we allocate each site an id.

i.e. Site A = 101 Site B = 102 Site C = 103

We then use the DLCI number of the site we intend to connect to.

Site A - DLCI 102 --FR Cloud -- DLCI 101 Site B Site A - DLCI 103 --FR Cloud -- DLCI 101 Site C

Site A uses 102 to reach Site B Site B uses 101 to reach Site A Site A uses 103 to reach Site C Site C uses 101 to reach Site A

You could still label the DLCI on the outgoing link but now as you know that all DLCI 101 go to Site A, all DLCI 102 to site B etc. you can just label the site instead.



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thanks Toby, FWI anyone else interested this thread has continued on

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