Method and apparatus for accommodating duplicate mac addresses

Abstract

Each access node is associated with one or more IP subnets with a preferred default subnet. Each subnet is instantiated as a unique virtual Ethernet broadcast domain. As client nodes register on the communication network, they will dynamically try to obtain an IP address for use on the communication network. As part of this process, the MAC address of the client node will be checked to ensure that it is not a duplicate of another MAC address associated with another client node that has already been assigned an IP address from the default subnet. When duplicate MAC addresses are detected, the device with the duplicate MAC address will be assigned an IP address from a different subnet so that more than one client device with the same MAC address are not associated with the same subnet.

1 . A method of allocating Internet Protocol (IP) addresses to client devices, the method comprising:
 receiving requests for IP addresses for a plurality of client devices, each client device being associated with a respective Media Access Control (MAC) address and with a respective facility having a respective default subnet; and   allocating respective IP addresses to the client devices based, at least in part, on the respective MAC addresses of the client devices, the allocated IP addresses for some of the client devices being associated with the respective default subnets of the facilities with which the some of the client devices are associated, and the allocated IP addresses for others of the client devices being associated with subnets different from the respective default subnets of the facilities with which the others of the client devices are associated.   
     
     
         2 . The method of  claim 1 , wherein client devices having a same MAC address are allocated respective IP addresses associated with different subnets. 
     
     
         3 . The method of  claim 2 , wherein allocating the respective IP addresses comprises, when the client devices having the same MAC address are associated with a same facility, allocating to one of the client devices having the same MAC address an IP address associated with a default subnet of the same facility and allocating to each other client device having the same MAC address an IP address associated with a respective subnet different from the default subnet of the same facility. 
     
     
         4 . The method of  claim 1 , wherein allocating the respective IP addresses comprises:
 for a client device for which an IP address has been requested, the client device being associated with a respective MAC address and a respective facility, determining whether another client device associated with a same MAC address and a same facility has currently been allocated an IP address associated with a default subnet of the same facility; and   when another client device associated with the same MAC address and the same facility has currently been allocated an IP address associated with the default subnet of the same facility, allocating an IP address associated with a subnet other than the default subnet of the same facility to the client device for which the IP address has been requested.   
     
     
         5 . The method of  claim 4  wherein allocating the respective IP addresses comprises, when another client device associated with the same MAC address and the same facility has not currently been allocated an IP address associated with the default subnet of the same facility, allocating an IP address associated with the default subnet of the same facility to the client device for which an IP address has been requested. 
     
     
         6 . The method of  claim 1 , wherein the requests for the IP addresses are received and the IP addresses are allocated by a centralized server. 
     
     
         7 . The method of  claim 6 , wherein the centralized server is a dynamic host configuration protocol (DHCP) server. 
     
     
         8 . The method of  claim 1 , wherein each facility is associated with a respective access node. 
     
     
         9 . The method of  claim 8 , wherein the each facility connects to the respective access node via a respective physical or virtual port of the respective access node. 
     
     
         10 . The method of  claim 8 , wherein each respective access node supports multiple facilities. 
     
     
         11 . A network element for allocating Internet Protocol (IP) addresses to client devices, the network element comprising:
 at least one communication interface configured to receive requests for IP addresses for client devices, each client device being associated with a respective Media Access Control (MAC) address and with a respective facility having a respective default subnet; and   at least one IP address allocation element configured to allocate respective IP addresses to the client devices, the allocated IP addresses for some of the client devices being associated with the respective default subnets of the facilities with which the some of the client devices are associated, and the allocated IP addresses for others of the client devices being associated with subnets different from the respective default subnets of the facilities with which the others of the client devices are associated.   
     
     
         12 . The network element of  claim 11 , wherein the at least one IP address allocation element is configured to allocate to client devices having a same MAC address respective IP addresses associated with different subnets. 
     
     
         13 . The network element of  claim 12 , wherein the at least one IP address allocation element is configured to allocate respective IP addresses by, when client devices having the same MAC address are associated with a same facility, allocating to one of the client devices having the same MAC address an IP address associated with a default subnet of the same facility and allocating to each other client device having the same MAC address an IP address associated with a respective subnet different from the default subnet of the same facility. 
     
     
         14 . The network element of  claim 11 , wherein the at least one IP address allocation element is configured to allocate respective IP addresses by:
 for a client device for which an IP address has been requested, the client device being associated with a respective MAC address and a respective facility, determining whether another client device associated with a same MAC address and a same facility has currently been allocated an IP address associated with a default subnet of the same facility; and   when another client device associated with the same MAC address and the same facility has currently been allocated an IP address associated with the default subnet of the same facility, allocating an IP address associated with a default subnet other than the default subnet of the same facility to the client device for which the IP address has been requested.   
     
     
         15 . The network element of  claim 14 , wherein the at least one IP address allocation element is configured to allocate respective IP addresses by, when another client device associated with the same MAC address and the same facility has not currently been allocated an IP address associated with the default subnet of the same facility, allocating an IP address associated with the default subnet of the same facility to the client device for which an IP address has been requested. 
     
     
         16 . The network element of  claim 11 , implemented in a centralized server. 
     
     
         17 . The network element of  claim 16 , implemented in a dynamic host configuration protocol (DHCP) server. 
     
     
         18 . The network element of  claim 17 , wherein the at least one IP address allocation element runs at least one DHCP process. 
     
     
         19 . The network element of  claim 17 , comprising a table containing associations between facilities and subnets assigned to the facilities. 
     
     
         20 . The network element of  claim 17 , comprising at least one table configured to associate MAC addresses with respective facilities and subnets.