Method and apparatus for simulating IP multinetting
View Patent ↗IP Multinetting on a local area network is simulated by performing VLAN translation at a port connecting to the local area network. This allows IP addresses from multiple subnets to be associated with a single VLAN on the Local Area Network (LAN), while allowing the core switch to process the packets with a one-to-one correspondence between IP Subnet and VLAN. When a packet is received from the local area network at an IP multinetting port, the VLAN ID will be read to determine if the packet contains the IP Multinetting VLAN ID. The IP Subnet address will also be checked to see if the packet is associated with an IP Subnet that is part of the Multinetting. If so, the multinetting VLAN ID will be changed to an IP Subnet specific VLAN ID before the packet is processed by the core switch. In the reverse direction, IP subnet specific VLAN IDs will be translated to the IP Multinetting VLAN ID.
1. A method of processing a packet at a network element, the method comprising the steps of:
receiving the packet at an Internet Protocol (IP) Multinetting port of the network element from a host over a local area network;
determining whether the packet contains a Virtual Local Area Network (VLAN) Identifier (ID) corresponding to an IP Multinetting VLAN ID on the local area network;
determining whether the packet has a source address included in one of a plurality of IP subnets assigned to the IP Multinetting VLAN ID; and
if the packet was received at the IP Multinetting port, contains the VLAN ID corresponding to the IP Multinetting VLAN ID, and the source address is included in one of the plurality of IP subnets assigned to the IP Multinetting VLAN ID, performing VLAN Translation so that the packet contains a VLAN ID of the one of the plurality of IP subnets instead of the IP Multinetting VLAN ID before passing the changed packet internally to be processed by the network element.
2. The method of claim 1 , further comprising the step of maintaining, by the network element, a table containing a one-to-one correspondence between VLAN ID and IP subnet.
3. The method of claim 2 , wherein the one-to-one correspondence between VLAN ID and IP subnet is such that addresses from at most one class C IP subnet will be assigned to hosts associated with the VLAN ID.
4. The method of claim 1 , wherein the network element has a built-in assumption that IP addresses from at most one IP subnet will be associated with any one VLAN ID.
5. The method of claim 1 , further comprising the step of configuring the port to support IP multinetting.
6. A method of supporting IP multinetting on a network element that has a data plane configured to require a one-to-one correspondence between IP subnet and VLAN ID, the method comprising the steps of:
receiving a packet by the network element at a first network port from an external network;
classifying the packet according to IP subnet to determine a first VLAN for the packet;
processing the packet within the first VLAN to determine an output port for the packet;
passing the packet to the output port;
determining whether the packet is to be transmitted on an IP multinetting VLAN at the output port; and
if the packet is to be transmitted on an IP multinetting VLAN, performing VLAN translation to change the first VLAN to a second VLAN, the second VLAN being associated with the IP multinetting VLAN so that the packet may be transmitted within the IP multinetting VLAN on an attached Local Area Network.
7. The method of claim 6 , wherein the step of determining whether the packet is to be transmitted on an IP multinetting VLAN comprises the step of determining whether the output port is a multinetting port.
8. The method of claim 7 , wherein a multinetting port is a port that has been administratively configured to perform VLAN ID translation to enable IP multinetting to be simulated on the attached Local Area Network.
9. The method of claim 8 , further comprising the step of determining whether the first VLAN is associated with the IP multinetting VLAN at the output port.
10. The method of claim 9 , further comprising the step of determining whether a destination IP address of the packet is within a class C IP subnet assigned to the multinetting VLAN.
11. A network element, comprising:
processing circuitry designed to process packets under an assumption that addresses from at most one class C IP subnet will be associated with a particular VLAN; and
a multinetting port configured to perform a VLAN translation by changing the particular VLAN to a VLAN associated with an IP multinetting VLAN on an attached Local Area Network such that hosts with IP addresses assigned from multiple class C IP subnets are able to participate in the IP multinetting VLAN on the LAN, while allowing the network element to process traffic from the hosts under the assumption that addresses from at most one class C IP subnet will be associated with the particular VLAN.
12. The network element of claim 11 , wherein the multinetting port is further configured to perform a series of checks on each packet to selectively perform VLAN translation only on packets that are associated with the IP multinetting VLAN.
13. The network element of claim 11 , further comprising a VLAN table accessible by the multinetting port to determine IP subnet specific VLAN values to be assigned to packets received from the IP multinetting VLAN on the LAN.