A. to map a known IP address to a MAC address B. to map a known DLCI to a MAC address C. to map a known MAC address to an IP address D. to map a known DLCI to an IP address E. to map a known IP address to a SPID F. to map a known SPID to a MAC address
Correct Answer: D
Dynamic address mapping relies on the Frame Relay Inverse Address Resolution Protocol (Inverse ARP), defined by RFC 1293, to resolve a next hop network protocol (IP) address to a local DLCI value. The Frame Relay router sends out Inverse ARP requests on its Frame Relay PVC to discover the protocol address of the remote device connected to the Frame Relay network. The responses to the Inverse ARP requests are used to populate an address-to-DLCI mapping table on the Frame Relay router or access server. The router builds and maintains this address-to-DLCI mapping table, which contains all resolved Inverse ARP requests, including both dynamic and static mapping entries.
What is the meaning of the term dynamic as displayed in the output of the show frame-relay map command shown?
A. The Serial0/0 interface is passing traffic. B. The DLCI 100 was dynamically allocated by the router. C. The Serial0/0 interface acquired the IP address of 172.16.3.1 from a DHCP server. D. The DLCI 100 will be dynamically changed as required to adapt to changes in the Frame Relay cloud. E. The mapping between DLCI 100 and the end station IP address 172.16.3.1 was learned through Inverse ARP.
Correct Answer: E
Inverse Address Resolution Protocol (Inverse ARP) was developed to provide a mechanism for dynamic DLCI to Layer 3 address maps. Inverse ARP works much the same way Address Resolution Protocol (ARP) works on a LAN. However, with ARP, the device knows the Layer 3 IP address and needs to know the remote data link MAC address. With Inverse ARP, the router knows the Layer 2 address which is the DLCI, but needs to know the remote Layer 3 IP address.
When using dynamic address mapping, Inverse ARP requests a next-hop protocol address for each active PVC. Once the requesting router receives an Inverse ARP response, it updates its DLCI-to-Layer 3 address mapping table. Dynamic address mapping is enabled by default for all protocols enabled on a physical interface. If the Frame Relay environment supports LMI autosensing and Inverse ARP, dynamic address mapping takes place automatically. Therefore, no static address mapping is required.