Method and system for detecting use of wrong internet protocol address

1. A non-transitory computer readable medium comprising instructions which, when executed by a processor, causes the processor to:

maintain a range of valid IP addresses for a particular IP subnet;

receive a message from a first wireless client device that uses a source IP address not authenticated for the particular IP subnet within the particular IP subnet by an access point on the particular IP subnet;

determine a source IP address in the message received on the particular IP subnet;

determine that the source IP address is not within the range of valid IP addresses for the particular IP subnet;

responsive at least to determining that the source IP address is not within the range of valid IP addresses for the particular IP subnet, transmit at least one message that causes the first wireless client device to request a new IP address that is within the valid IP addresses.

2. The non-transitory computer readable medium of claim 1 , further comprising instructions to:

snoop a DHCP message transmitted to a second wireless client device on the particular IP subnet; and

based on the DHCP message, identify the range of valid IP addresses on the particular IP subnet.

3. The non-transitory computer readable medium of claim 2 , wherein instructions to identify the range of valid IP addresses on the particular IP subnet in the DHCP message comprise instructions to determine a subnet mask, corresponding to the particular IP subnet, indicated in the DHCP message and identify the range of valid IP addresses on the particular IP subnet based on the subnet mask.

4. The non-transitory computer readable medium of claim 3 , wherein instructions to receive the message from the first wireless client device is performed subsequent to the first wireless client device being assigned the source IP address while on a second IP subnet and roaming from the second IP subnet to the particular IP subnet.

5. The non-transitory computer readable medium of claim 2 , wherein the DHCP message is a DHCP acknowledgement message.

6. The non-transitory computer readable medium of claim 2 , wherein the DHCP message is a DHCP offer message.

7. The non-transitory computer readable medium of claim 1 , wherein the range of valid IP addresses for the particular IP subnet is determined by snooping a message on the particular IP subnet.

8. The non-transitory computer readable medium of claim 1 , wherein the range of valid IP addresses for the particular IP subnet is determined based on configuration stored at a network device on the particular IP subnet.

9. The non-transitory computer readable medium of claim 1 , wherein the range of valid IP addresses for the particular IP subnet is determined by snooping a route advertisement message.

10. The non-transitory computer readable medium of claim 1 , wherein the at least one message comprises a De-Association message and a De-Authentication message.

11. The non-transitory computer readable medium of claim 1 , wherein the at least one message comprises a De-Association message sent to the wireless client device.

12. The non-transitory computer readable medium of claim 1 , wherein the at least one message comprises a De-Authentication message.

13. The non-transitory computer readable medium of claim 12 , wherein the de-authentication message is transmitted to a second network device storing authentication information corresponding to the wireless client device.

14. A system comprising:

at least one device including a hardware processor;

the system to perform operations comprising:

maintaining a range of valid IP addresses for a particular IP subnet;

receiving a message from a first wireless client device by an access point on the particular IP subnet;

determining a source IP address in the message received on the particular IP subnet;

determining that the source IP address is not within the range of valid IP addresses for the particular IP subnet without modifying the source IP address prior to determining that the source IP address is not within the range of valid IP addresses; and

responsive at least to determining that the source IP address is not within the range of valid IP addresses for the particular IP subnet, transmitting at least one message that causes the first wireless client device to request a new IP address that is within the valid IP addresses.

15. The system of claim 14 , wherein to maintain the range of valid IP addresses comprises:

to snoop a DHCP message transmitted to a second wireless client device on the particular IP subnet; and

based on the DHCP message, to identify the range of valid IP addresses on the particular IP subnet.

16. The system of claim 15 , wherein to identify the range of valid IP addresses on the particular IP subnet in the DHCP message comprises to determine a subnet mask, corresponding to the particular IP subnet, indicated in the DHCP message and identifying the range of valid IP addresses on the particular IP subnet based on the subnet mask.

17. The system of claim 16 , wherein the message from the first wireless client device is received subsequent to the first wireless client device being assigned the source IP address while on a second IP subnet and roaming from the second IP subnet to the particular IP subnet.

18. The system of claim 15 , wherein the DHCP message comprises one of a DHCP acknowledgement message and a DHCP offer message.

19. The system of claim 14 , wherein the range of valid IP addresses for the particular IP subnet is determined either (a) by snooping a message on the particular IP subnet, or (b) by snooping a route advertisement message, or (c) based on a configuration stored at a network device on the particular IP subnet.

20. The system of claim 14 , wherein the at least one message comprises a De-Association message and/or a De-Authentication message.