Frame Relay quick question

mobri09

When your setting up frame relay point to point. Are you suppose to use the REMOTE or LOCAL DLCI number. It seems like sybex saids one and cisco press saids otherwise.
I would assume it would be your local DLCI # for the point to point.

dtlokee

It needs to be the local DLCI, the DLCI identifies the PVC used to send frames to the remote end. When the frame switch receives the frame it looks at the DLCI in the frame relay header to determine where to switch the frame next.

mobri09

What about for multipoint...would this be the remote DLCI #

dtlokee

No it will still use the local DLCI. If you're using multipoint the service provider needs to provision a single virtual circuit for each remote site, each VC will have it's own DLCI.

bighornsheep

local or remote DLCI where?

When you use frame-relay interface-dlci dlci this is the local dlci number that you are specifying in the vc.

When you use frame-relay map protocol protocol-address dlci this is the remote dlci number for the remote ip that you are mapping in the vc.

mobri09

I am very confused. Look on page 423 press ICND and it is specifying remote DLCI numbers

dtlokee

I think I know the diagram you are referring to, some of my students have shown it to me and it's confusing, it seems to show the DLCI's at the remot routers but you must specify the DLCI for the local end of the PVC, not the remote end of the PVC.so say you had 4 routers, R1, R2, R3, R4 and R1 is the hub.

R1 has a 1 PVC to R2 one to R3, one to R4

R1 is uding DLCI 102 to R2
R1 is using DLCI 103 to R3
R1 is using DLCI 104 to R4

The configuration of the hub would use the local DLCI:

Interface serial 0/0
encap frame-relay
no frame-relay inverse-arp
ip address 192.168.1.1 255.255.255.248
frame-relay map ip 192.168.1.1 102                 !<--- Only needed to ping the local interface
frame-relay map ip 192.168.1.2 102 broadcast
frame-relay map ip 192.168.1.3 103 broadcast
frame-relay map ip 192.168.1.4 104 broadcast

And R2 is a spoke using DLCI 201 to get to R1

interface serial 0/0
encap frame-relay
no frame-relay inverse-arp
ip address 192.168.1.2 255.255.255.248
frame-relay map ip 192.168.1.1 201 broadcast
frame-relay map ip 192.168.1.2 201         !<--- only needed to ping the local interface
frame-relay map ip 192.168.1.3 201 
frame-relay map ip 192.168.1.4 201

R3 and R4 would be the same as R2 just change the DLCI for the PVC to the hub

mobri09

thanks for all the help. I still have a few questions.
Wouldn't you be using a Multipoint connection on R1 (hub)
Wouldn't R1 also need the frame-relay interface DLCI 201 command also.
Also why would you disable inverse arp...you should just let it do all the work and find the mappings right?

dtlokee

The physical interface is "multipoint" even though I didn't create a subinterface it is still multipoint, and the "frame-realy interface-dlci" command is used on point-to-point subinterfaces, or if you have more than one multipoint interface on the same physical interface to apply the DLCI to the correct subinterface (there are other uses but that is what is in CCNA)

mobri09

If you wanted to could you HAVE created multipoint subinterfaces?

dtlokee

Yes, it will work either way. You only need to create a single multipoint subinterface on each router.

mobri09

Thanks for all your help and time on this one