Method and system for subnetting in a switched IP network
First Claim
1. A switch for providing a data link layer switching function between distinct subnetworks of a data communications system having a plurality of interconnected subnetworks for enabling end stations on the distinct subnetworks to communicate directly without the use of router devices, the switch comprising:
- a subnet mask and a plurality of subnets specified by a user via a user interface, the subnet mask being larger in value than a subnet mask of a source end station on a first distinct subnetwork, said source end station having a network layer address, and a data link layer address, the subnet mask of the switch also being larger in value than a subnet mask of a destination end station on a second distinct subnetwork, said destination end station having a network layer address, and a data link address;
packet analysis and forwarding programming code, operating on a processing unit in said switch, for analyzing a multicast packet, having both network layer information and a medium access control (MAC) address, received from said source end station, and selectively forwarding said multicast packet to all ports associated with a destination subnet; and
a subnet to port mapping table for storing a mapping of said plurality of subnets to a plurality of ports associated with each said subnet;
the packet analysis and programming code also analyzing the MAC address of the multicast packet to make a determination of whether the packet is an all stations multicast message, and if the code determines that the multicast packet is an all stations multicast message, the code then analyzes the network layer information to determine whether the multicast packet is an address resolution protocol packet, and if the code determines that the multicast packet is an address resolution protocol packet, the code then makes a forwarding decision for the multicast packet based upon subnet information derived from the network layer information.
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Abstract
A large flat IP network is created in a switched layer-2 network by adjusting the subnet masks of hosts such that these hosts can communicate directly with other hosts without the use of an intermediate router. The layer-2 switches are configured with user-selected IP subnets and monitor and analyze multicast packets to learn the mapping between IP subnets and switch ports. The layer-2 switches selectively forward the mulitcast packets based on the learned mappings between IP subnets and ports. After the destination host responds to the forwarded multicast, a direct connection is established between the source and destination hosts using the media access control addresses of both hosts.
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Citations
20 Claims
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1. A switch for providing a data link layer switching function between distinct subnetworks of a data communications system having a plurality of interconnected subnetworks for enabling end stations on the distinct subnetworks to communicate directly without the use of router devices, the switch comprising:
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a subnet mask and a plurality of subnets specified by a user via a user interface, the subnet mask being larger in value than a subnet mask of a source end station on a first distinct subnetwork, said source end station having a network layer address, and a data link layer address, the subnet mask of the switch also being larger in value than a subnet mask of a destination end station on a second distinct subnetwork, said destination end station having a network layer address, and a data link address;
packet analysis and forwarding programming code, operating on a processing unit in said switch, for analyzing a multicast packet, having both network layer information and a medium access control (MAC) address, received from said source end station, and selectively forwarding said multicast packet to all ports associated with a destination subnet; and
a subnet to port mapping table for storing a mapping of said plurality of subnets to a plurality of ports associated with each said subnet;
the packet analysis and programming code also analyzing the MAC address of the multicast packet to make a determination of whether the packet is an all stations multicast message, and if the code determines that the multicast packet is an all stations multicast message, the code then analyzes the network layer information to determine whether the multicast packet is an address resolution protocol packet, and if the code determines that the multicast packet is an address resolution protocol packet, the code then makes a forwarding decision for the multicast packet based upon subnet information derived from the network layer information. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method implemented by a switch for enabling source and destination end stations to communicate directly, without the use of router devices, in a data communication system having a plurality of interconnected subnetworks, the switch providing a data link layer switching function between a source end station on a first subnetwork and a destination end station on a second subnetwork, the method comprising:
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specifying in the switch a plurality of subnets for said data communication system and a subnet mask, the subnet mask being larger in value than a subnet mask specified at the source end station, the subnet mask in the switch also being larger in value than a subnet mask specified in the destination end station;
determining each port of the switch associated with each of said plurality of subnets in said data communication system;
analyzing at the switch a multicast packet, having both network layer information and a Medium Access Control (MAC) address, received from said source end station to determine the ports associated with a destination subnet; and
selectively forwarding at the switch said multicast packet to said ports associated with said destination subnet;
analysis of the multicast packet including determining whether the MAC address indicates that the multicast packet is an all stations multicast message, and if the multicast packet is an all stations multicast message, the method also includes analyzing the network layer information to determine whether the multicast packet is an address resolution protocol packet, and if the multicast packet is an address resolution protocol packet, a forwarding decision is made for the multicast packet based upon subnet information derived from the network layer information. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A switch for providing a data link layer switching function in a communication system having a plurality of interconnected subnetworks, the system including a source end station on a first subnetwork and a destination end station on a second subnetwork, the switch comprising:
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means for specifying a plurality of subnets for said data communication system and a subnet mask in said switch, the subnet mask being larger in value than a subnet mask specified in the source end station;
means for determining each port associated with each of said plurality of subnets in said data communication system;
means for analyzing a multicast packet, having both network layer information and a medium access control (MAC) address, received from said source end station to determine the ports associated with a destination subnet; and
means for selectively forwarding said multicast packet to said ports associated with said destination subnet;
the means for analyzing including means for determining if the multicast packet is an all stations multicast message, and means for analyzing the network layer information to determine whether the multicast packet is an address resolution protocol packet, and means for making a forwarding decision, if the multicast packet is an address resolution protocol packet, for the multicast packet based upon subnet information derived from the network layer information. - View Dependent Claims (17, 18, 19, 20)
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Specification