Patent ID: 8572217
Filing Date: 2013-10-29
Classification: H04L

Abstract:
1. A method in a network element to enable clientless IP services (CLIPS) for a Dynamic Host Configuration Protocol (DHCP) client on a last-resort interface comprising: receiving, over a network, on the last-resort interface of the network element a request packet containing a request for an IP address, the request packet originating from the DHCP client, wherein the request packet passes through a DHCP relay located between the network element and one or more DHCP client subnets, wherein the request packet includes a GI address field having an IP address of an interface of the DHCP relay, and wherein the interface of the DHCP relay is at located within the DHCP relay; in response to the request packet, on behalf of the DHCP client, forwarding a modified request packet to a set of one or more DHCP servers, the modified request packet including an IP address of the last-resort interface in the GI address field; receiving a response packet forwarded from one of the DHCP servers of the set of DHCP servers, the response packet at least including an IP address to be allocated to the DHCP client, a default network gateway address of the DHCP server, and a gateway IP (GI) address field having the IP address of the last-resort interface; processing the received response packet by-passing the DHCP relay located between the DHCP client and the network element; responding to the DHCP client with respect to the request packet as if the network element is an IP address provider, on behalf of the DHCP server; intercepting an Address Resolution Protocol (ARP) request originated from the DHCP client and destined for the DHCP server that requests a Media Access Control (MAC) address corresponding with the default network gateway address of the DHCP server; and communicating to the DHCP client, in response to intercepting the ARP request, an ARP acknowledgement packet that includes a MAC address of the network element; checking a learned router identification (RID) data structure to determine whether the learned RID was previously learned, the previously learned RID having been previously placed within a learned RID data structure; and if the learned RID is not already located within the learned RIDs data structure: placing the learned RID into the learned RIDs data structure to enable the network element to alias for the DHCP server; and placing the learned RID into an Address Resolution Protocol (ARP) data structure to enable the network element to respond to ARP queries from the DHCP client, the ARP queries required for the DHCP client to obtain a MAC address to enable clientless IP services on the last-resort interface.