Static Frame Relay Mapping

You can statically configure the same mapping information instead of using Inverse ARP.  In a production network, you would just go ahead and use Inverse ARP, probably.  For the exams, you need to know how to configure the static map command statements.

Mapping is needed for each next-hop Layer 3 address for each Layer 3 protocol being routed.  The broadcast keyword is required when the router needs to send broadcasts or multicasts to the neighboring router – for example, to support routing protocol messages such as Hellos.

A Partially Meshed Network with One IP Subnet Per VC

Cisco IOS needs to associate the correct PVC with the correct subinterface.  This is accomplished with the frame-relay interface-dlci command.

The subinterface numbers do not have to match on the router on the other end of the PVC, nor does the DLCI number.

Assigning a DLCI to a Particular Subinterface

When configuring subinterfaces, the DLCIs must be associated with each subinterface in one of two ways.  frame-relay interface dlci subinterface subcommand or the frame-relay map command as a interface subcommand.  This command would both associate a DLCI with the subinterface and statically configure a mapping of Layer 3 next-hop IP address to that DLCI.

The router disables Inverse ARP on a subinterface when the frame-relay map command is configured.  When using static maps on the router on one end of the VC, keep in mind that the router on the other end of the VC will not receive any Inverse ARP messages and may also then need to be configured with the frame-relay map command.