LMI DLCI's

Answered Question
Sep 28th, 2004

I understand about local and global DLCI's, but I'm confused with where LMI DLCI's come into play. I know there is basic Frame Relay and LMI Frame Relay. Am I correct in assuming that thereare two DLCI numbers in the LMI Frame Relay? Are both sent in the frame? Where is the LMI DLCI number located in a frame. Not very clear on this concept. Do I even need to worry about this for the CCNA?

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Correct Answer by tiknapp about 9 years 6 months ago

Hi,

If you have a normal frame-relay connection, you'll have LMI configured (with transport on the associated DLCI) and a DLCI assigned from the carrier (for data transport). You don't configure the LMI DLCI when you set this up, you'll just configure the LMI type. You'll configure the data DLCI with the command "frame-relay interface-dlci". So you can consider them independent in one way, but they rely on each other. Without keepalives (LMI) the sub/int is going to go down and you won't be able to transmit on the DLCI for your data.

Hope this helps,

Tim

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tiknapp Tue, 09/28/2004 - 11:28

Hello Chris,

Annex d & q933a are on DLCI 0, Cisco LMI is on DLCI 1023. Check out this link it contains the LMI format you are looking for.

http://www.cisco.com/en/US/tech/tk713/tk237/technologies_tech_note09186a0080094183.shtml

...also look towards the bottom there's another link that will take you to univercd doc containing even more detailed information about the LMI frame format.

c.gierula Tue, 09/28/2004 - 12:54

So if you ar using standard Frame Relay you have local and global DLCI's and if you are using Frame Relay that conforms to the LMI standard you use LMI DLCI's only? I guess I'm looking for the relationship (or lack of) between them.

Correct Answer
tiknapp Tue, 09/28/2004 - 23:10

Hi,

If you have a normal frame-relay connection, you'll have LMI configured (with transport on the associated DLCI) and a DLCI assigned from the carrier (for data transport). You don't configure the LMI DLCI when you set this up, you'll just configure the LMI type. You'll configure the data DLCI with the command "frame-relay interface-dlci". So you can consider them independent in one way, but they rely on each other. Without keepalives (LMI) the sub/int is going to go down and you won't be able to transmit on the DLCI for your data.

Hope this helps,

Tim

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Posted September 28, 2004 at 9:20 AM
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