DLCI local and global

AceAll

Can anyone please tell me the difference between local and global DLCI used in the frame-relay networks ?

2lazybutsmart

The DLCIs are usually assigned by the providers, so they are locally significant to a particular circuit. The only way you would have global DLCIs is if you owned the whole frame-relay network. Like if you created your own frame-relay lab

Sumutai

A local DLCI is the number a router uses to tell a Frame Relay switch which Virtual Circuit to use.

Because these numbers are only used between the router and the switch to which it is connected, they are said to be local.

Local DLCIs can be any number, but each one must be unique within the router. However, routers on the other side of the network also use DLCIs, which can be the same numbers as those used in the original router, but pointing to different VCs, as they are only locally significant.

This can be confusing for an engineer, so a method called Global DLCIs is often used.

In your FR network you would give each router a UNIQUE DLCI. All other routers would use this DLCI value to send frames to that router.

Hence, a DLCI on any router in your network with a value of 40 say would always point to the same receiving router. (obviously the receiving router in this case would not use DLCI 40).

This makes the addressing scheme a little more LAN-like, but is not neccessary for a Frame Relay network to work.

Hope this helps.

vidalch

There are a few ways to number DLCIs. I believe four different ways.

Primary / Secondary mapped on each end switch. Basically, 2 on this side, two on the distant side.

Global, same throughout the pvc.

The two others escape me now. I need to go through a bunch of documentation to see if I can find the other two.

However, carriers / ISP's are really the only ones concerned with the significance of the number system.

I too, after 24 years working in the industry, am preparing for the CCNA exam. I havent see any questions related to the actualy numbering scheme.

Im at school now, when I get home, I'll look through a few cd's I have to see if I can find it for you.

Regards
Chris

vidalch

ps

Ex AT&T

AceAll

thank you very much !!!

vidalch

Hello,

Didnt forget about you ... still looking through my cd's. Got lots ....

Yankee

There's a lil bit of misleading info in this thread. A DLCI need not be unique to a router, but it must be unique to a physical interface. This is true at the carrier end too, where is doesn't have to be unique to the frame switch but must be to the port it is assigned.

Hope this doesn't confuse people.

Yankee