Global & Local DLCI in FR

Unanswered Question
Jul 30th, 2009

Hello,

I am very confused about Local and Global DLCI.

I am attaching what the example I read and marked in red two things that are confusing me. The book says the figure shows Global DLCIs but then it statkes that "on any given router, only Local DLCI values are in the configuration or show commands". If the diagram shows Global addresses... then why in the configuration and in the show command (shown in the attachement) we can see those DLCI's? Please help make this clear!

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Giuseppe Larosa Thu, 07/30/2009 - 12:20

Hello Francisco,

Global addressing is a convention that pretends that DLCIs are like MAC addresses.

all FR DTE routers use the same DLCI X to reach remote site x.

This is done by FR service providers with some arrangements in the choice of DLCI values on the access links.

However, each DLCI is locally significant.

the sentences that you have hightlighted just says that:

if you see a network diagram where there are multiple routers if only a DLCI is shown near each router this means that is the DLCI value that all other routers will use on their access link to reach that router (like a MAC address)

However, from a technical point of view DLCI are locally significant and DLCIs listed in sh frame-rel pvc are local on access link and signalled by LMI between router interface and FR switch port.

DLCI changes at each FR switch hop in a transparent way for users.

Hope to help

Giuseppe

fjcardenas-1 Fri, 07/31/2009 - 12:29

After reading the book once and again, now I understand what you mean. I think I got it. Thanks.

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