Cisco IOS Wide-Area Networking Configuration Guide - Free Books

Configuring Frame RelayCustomizing Frame Relay for Your NetworkAddressing on Multipoint SubinterfacesIf you specified a multipoint subinterface in the preceding procedure, perform the configuration tasks inthe following sections:• Accepting Inverse ARP for Dynamic Address Mapping on Multipoint Subinterfaces• Configuring Static Address Mapping on Multipoint SubinterfacesYou can configure some protocols for dynamic address mapping and others for static address mapping.Accepting Inverse ARP for Dynamic Address Mapping on Multipoint SubinterfacesDynamic address mapping uses Frame Relay Inverse ARP to request the next-hop protocol address fora specific connection, given a DLCI. Responses to Inverse ARP requests are entered in anaddress-to-DLCI mapping table on the router or access server; the table is then used to supply thenext-hop protocol address or the DLCI for outgoing traffic.Since the physical interface is now configured as multiple subinterfaces, you must provide informationthat distinguishes a subinterface from the physical interface and associates a specific subinterface witha specific DLCI.To associate a specific multipoint subinterface with a specific DLCI, use the following command ininterface configuration mode:CommandRouter(config-if)# frame-relayinterface-dlci dlciPurposeAssociates a specified multipoint subinterface with a DLCI.Inverse ARP is enabled by default for all protocols it supports, but can be disabled for specificprotocol-DLCI pairs. As a result, you can use dynamic mapping for some protocols and static mappingfor other protocols on the same DLCI. You can explicitly disable Inverse ARP for a protocol-DLCI pairif you know the protocol is not supported on the other end of the connection. See the section “Disablingor Reenabling Frame Relay Inverse ARP” later in this chapter for more information.Because Inverse ARP is enabled by default for all protocols that it supports, no additional command isrequired to configure dynamic address mapping on a subinterface.For an example of configuring Frame Relay multipoint subinterfaces with dynamic address mapping, seethe section “Frame Relay Multipoint Subinterface with Dynamic Addressing Example” later in thischapter.Configuring Static Address Mapping on Multipoint SubinterfacesA static map links a specified next-hop protocol address to a specified DLCI. Static mapping removesthe need for Inverse ARP requests; when you supply a static map, Inverse ARP is automatically disabledfor the specified protocol on the specified DLCI.You must use static mapping if the router at the other end either does not support Inverse ARP at all ordoes not support Inverse ARP for a specific protocol that you want to use over Frame Relay.To establish static mapping according to your network needs, use one of the following commands ininterface configuration mode:35