Certain devices use the Reverse Address Resolution Protocol (RARP) to obtain an IP address from a RARP server. MAC address information for the port is broadcast on all ports associated with an IP protocol-based or port-based VLAN. To enable a device to request an IP address from a RARP server outside its IP VLAN, you must create a RARP protocol-based VLAN.
RARP has the format of an ARP frame but its own Ethernet type (8035). You can remove RARP from the IP protocol-based VLAN definition and treat it as a separate protocol, thus creating a RARP protocol-based VLAN.
A typical network topology provides desktop switches in wiring closets with one or more trunk ports that extend to one or more data center switches where attached servers provide file, print, and other services. Use RARP functionality to define all ports in a network that require access to a RARP server as potential members of a RARP protocol-based VLAN. You must define all tagged ports and data center RARP servers as static or permanent members of the RARP VLAN. Therefore, a desktop host broadcasts an RARP request to all other members of the RARP VLAN. In normal operation, these members include only the requesting port, tagged ports, and data center RARP server ports. Because all other ports are potential members of this VLAN and RARP is only transmitted at startup, all other port VLAN memberships expire. With this feature, one or more centrally located RARP servers extend RARP services across traditional VLAN boundaries to reach desktops globally.