Configuring a Static Frame Relay Map
Cisco routers support all network layer protocols over Frame Relay, such as IPv4, IPv6, IPX, and AppleTalk. The address-to-DLCI mapping can be accomplished either by dynamic or static address mapping.
Dynamic mapping is performed by the Inverse ARP feature. Because Inverse ARP is enabled by default, no additional command is required to configure dynamic mapping on an interface. Figure 1 shows the topology used for this topic.
Static mapping is manually configured on a router. Establishing static mapping depends on your network needs. To map between a next hop protocol address and a DLCI destination address, use the frame-relay map protocol protocol-address dlci [broadcast] command, as shown in Figure 2. Notice the broadcast keyword at the end of the command.
Frame Relay, ATM, and X.25 are non-broadcast multiaccess (NBMA) networks. NBMA networks allow only data transfer from one computer to another, over a VC, or across a switching device. NBMA networks do not support multicast or broadcast traffic, so a single packet cannot reach all destinations. This requires you to replicate the packets manually to all destinations. Using the broadcast keyword is a simplified way to forward routing updates. The broadcast keyword allows IPv4 broadcasts and multicasts to be propagated to all nodes. It also allows IPv6 multicasts over the PVC. When the keyword is enabled, the router converts the broadcast or multicast traffic into unicast traffic so that other nodes receive the routing updates.
Figure 3 shows how to use the keywords when configuring static address maps. Notice that the first IPv6 Frame Relay map to a global unicast address does not include the broadcast keyword. However, the broadcast keyword is used in the mapping to the link-local address. IPv6 routing protocols use link-local addresses for multicast routing updates; therefore, only the link-local address map requires the broadcast keyword to forward multicast packets.
The example only shows the configurations to map the VCs between R1 and R2.
Note: Some routing protocols may require additional configuration options. For example, RIP, EIGRP, and OSPF require additional configurations to be supported on NBMA networks.