Wednesday, November 18, 2009
CCNA Fully Meshed Frame Relay Network Lab
I was a little bored this evening so I decided to get my hands dirty and try out a Fully-Meshed Frame Relay Network. It was actually a lot simple then I expected but I actually drew out a diagram before hand so i could picture in my head exactly how each VC was setup and with what DLCI. Something I have been kinda messing up is not using proper network design when creating my Frame-Relay networks. Previously I had been assigning the Point-to-Point Frame Relay router multiple DLC's that corresponded to each respective Point-to-Point link. I should have assigned one DLCI per DTE device but in my mind I could never picture how it worked so today I drew it out to help get my head wrapped around how it works.
DLCI's are locally significant between each DCE and DTE on a Frame Relay network. No other DTE knows what the other DTE use's as it's DLCI mapping to other DTE devices. So in this way you can logically have one DLCI mapping for every DTE so when configuring or reviewing the Frame-Relay network, it will be a lot easier to logically figure out which VC's go where. I actually managed to set everything up without any problems. The nice thing about LMI's is that the FR Switch (DCE) and the Router (DTE) sends LMI messages to each other that reports what DLCI's should be to reach the other DTE devices in the Frame Relay network. Each access link (DTE to DCE) reports LMI messages for their link but again the other access links could care less what DLCI's are setup for any other access links besides its own. As you can see in the GNS3 diagram I have setup this Fully-Meshed network with one IP subnet on the WAN connections and a VC between each device. I have also designed the network in such away that there is only one reported DLCI on each device!