Apparatus and method for preventing one way connectivity loops in a computer network

• US 7,076,594 B2
• Filed: 12/22/2000
• Issued: 07/11/2006
• Est. Priority Date: 12/22/2000
• Status: Expired due to Fees

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Gai, Silvano, Mahajan, Umesh, Benedetto, Marco Di
• Primary Examiner(s): Dang, Khanh
• Assistant Examiner(s): PHAN, RAYMOND NGAN
• Application Number:
  US09/747,676
• Publication Number:
  US 20040221087A1
• Time in Patent Office: 2,027 Days
• Field of Search: 710/311, 710316-317, 709/227, 709/238, 709239-244, 370/254, 370/292, 370/362, 370/399, 370/412, 370/256, 370220-221, 370/238, 370/252, 370/408
• US Class Current: 710/316
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00
• CPC Class Codes: H04L 45/48 Routing tree calculation

Abstract

Ports of a switch are assigned by a person, for example a network manager, to be for communication up the spanning tree toward the root switch (“up ports”), or down the spanning tree away from the root switch (“down ports”). This assignment is made by enabling “Uplinkguard” status for a desired up port, and by connecting the desired port to a switch which it is desired to place in the higher layer of the spanning tree. A port having Uplinkguard enabled is prevented, for example by software or firmware in its switch, from transitioning to a designated role. Uplinkguard-enabling a port, by preventing the port from transitioning to the designated role, has at least two consequences: preventing the port from being selected by the STP to transmit to lower switches in the spanning tree; and, preventing the port from transmitting when a one way connectivity fault develops on that port. A port with Uplinkguard enabled may transition to root port role. In the event that there is one way connectivity from a port, that port will not receive BPDU messages, and if the port is in blocked state, it will believe that it should take over and become the designated port for the external link to which it is connected. Uplinkguard prevents the port from transitioning to designated role. When the port attempts to transition into designated role, Uplinkguard forces the port to transition into blocked role, thereby eliminating formation of loops caused by one way connectivity faults.

Claims

1. A layer 2 switch, comprising:

a plurality of ports, at least one port of said plurality of ports capable of being set to a status of uplinkguard enabled (UG status);

first circuits for running the spanning tree protocol (STP) in said layer 2 switch, said STP capable of selecting said at least one port as either a designated port or as a root port;

second circuits for running uplinkguard enabled process, and said uplinkguard enabled process determining whether or not a port set to UG status has been selected by STP as a designated port; and

, blocking circuits to set said at least one port into blocked state, said blocking circuits setting said at least one port into blocked state in response to said at least one port being both in uplinkguard enabled status and selected by STP as a designated port.

2. The layer 2 switch of claim 1 further comprising:

said blocking circuits not setting said at least one port into a blocked status if said at least one port is to be selected by STP as a root port.

3. The layer 2 switch of claim 1 further comprising:

said first circuits removing said at least one port from a list of ports examined by STP if said port is in the blocked state and then rerunning STP.

4. A layer 2 switch, comprising:

a plurality of ports, at least one port of said plurality of ports capable of being set to a status of Uplinkguard enabled (UG status);

first circuits for maintaining said at least one port in blocked status, and for transitioning said port into forwarding status;

second circuits for running Uplinkguard enabled process, and said Uplinkguard enabled process determining whether or not a port set to UG status has been transitioned to forwarding status; and

,

blocking circuits to set said at least one port into blocked state, said blocking circuits setting said at least one port into blocked state in response to said at least one port being both in UG enabled status and transitioned into forwarding status, and said at least one port not being a root port when in forwarding status.

5. A method of managing a switch for use in a computer network, comprising:

providing a plurality of ports, at least one port of said plurality of ports capable of being set to a status of uplinkguard enabled status (UG status);

setting said at least one port to UG status;

running a spanning tree protocol (STP) in said switch, said STP capable of selecting said at least one port as either a designated port or as a root port;

running uplinkguard enabled process, and said uplinkguard process determining whether or not a port set to UG status has been selected by STP as a designated port; and

,

setting said at least one port into blocked status, in response to said at least one port being both in uplinkguard enabled status and selected by STP as a designated port.

6. The method of claim 5 further comprising:

not setting said at least one port into a blocked status if said at least one port is to be selected by STP as a root port.

7. The method of claim 5 further comprising:

removing said at least one port from a list of ports examined by STP if said port is in the blocked state and then rerunning STP.

8. A method of managing a switch for use in a computer network, comprising:

providing a plurality of ports, at least one port of said plurality of ports capable of being set to a status of uplinkguard enabled (UG status);

setting said at least one port to UG status, said at least one port being in blocking status;

transitioning said at least one port from blocking status to forwarding status;

determining whether or not said at least one port set to UG status has been transitioned to forwarding status, and if said at least one port is not a root port; and

setting said at least one port into blocked state in response to said at least one port being both in UG status and transitioned into forwarding status, and said at least one port not being a root port.

9. A data structure stored in a memory of a computer network switch, said data structure having entries, said entries having a “

state”

field and a “

role”

field, said state field having the value of “

blocked”

or the value of “

forwarding”

, comprising;

a first entry having the role field set to “

root port” and

the state field set to forwarding;

a second entry having the role field set to “

designated port” and

the state field set to forwarding;

a third entry having the role field set to “

blocked port” and

the state field set to blocked; and

,

a fourth entry having the role field set to “

uplinkguard enabled” and

the state field set to blocked.

10. A computer readable memory device, comprising:

said computer readable memory device containing instructions for practice of the method of

managing a switch for use in computer network, the method having,

providing a plurality of ports, at least one port of said plurality of ports capable of being set to a status of uplikguard enabled status (UG status);

setting said at least one port to UG status;

running a spanning tree protocol (STP) in said switch, said STP capable of selecting said at least one port as either a designated port or as a root port;

running uplinkguard enabledp process, and said uplinkguard process determining whether or not a port to UG status has been selected by STP as a designated port; and

,

setting said at least one port into blocked status, in response to said at least one port being both in uplinkguard enabled status and selected by STP as a designated port.

11. A network switch, comprising:

a plurality of ports, at least one port of said plurality of ports having a status, said status being set to a status of capable of transmitting to other switches lower in a spanning tree protocol (hereinafter STP), OR being set to a status of NOT being able to transmit to other switches lower in the STP (hereinafter referred to as uplinkguard enabled status, or UG status);

first circuits for running the spanning tree protocol (STP) in said network switch, said STP capable of selecting said at least one port as either a designated port or as a root port;

second circuits for running an uplinkguard enabled process, and said uplinkguard enabled process determining whether or not a port set to UG status has been selected by STP as a designated port; and

,

blocking circuits to set said at least one port into blocked state, said blocking circuits setting said at least one port into blocked state in response to said at least one port being both in UG status and selected by STP as a designated port.

12. The switch as in claim 11, further comprising:

a memory;

a data structure stored in the memory, said data structure having entries, said entries having a “

state”

field and a “

role”

field, said state field having the value of “

blocked”

or the value of “

forwarding”

;

a first entry having the role field set to “

root port”

and the state field set to forwarding;

a second entry having the role field set to “

designated port” and

the state field set to forwarding;

a third entry having the role field set to “

blocked port” and

the state field set to forwarding;

a third entry having the role field set to blocked; and

,

a fourth entry having the role field set to “

uplinkguard enabled” and

the state field set to blocked.

13. The switch as in claim 11, further comprising:

said blocking circuits not setting said at least one port into a blocked status if said at least one port is selected by STP as a root port.

14. The switch as in claim 11, further comprising:

said first circuits removing said at least one port from a list of ports examined by STP is said port is in the blocked state and when running STP.

15. A network switch, comprising:

first circuits for maintaining said at least one port in blocked status, and for transitioning said port into forwarding status;

second circuits for running Uplinkguard enabled process, and said Uplinkguard enabled process determining or not a port set to UG status has been transitioned to forwarding status; and

,

blocking circuits to set said at least one port into blocked state, said blocking circuits setting said at least one port into blocked state is response to said at least one port being both in UG enabled status and transitioned into forwarding status, and said at least one port not being a root port when in forwarding status.

16. A method for operating a network switch, comprising:

setting a status at for at least one port of a plurality of ports, said status being set to either a status of capable of transmitting to other switches lower in spanning tree protocol (spanning tree protocol is hereinafter STP), OR being set to a status of NOT being able to transmit to other switches lower in the STP (hereinafter referred to as uplinkguard enabled status, or UG status);

setting said at least one port to UG status;

running the spanning tree protocol (STP) in said network switch, said STP capable of selecting said at least one port as either a designated port or as a root port;

running an uplinkguard enabled process and said uplinkguard enabled process determining whether or not a port set to UG status has been selected by STP as a designated port; and

,

setting said at least one port into blocked state in response to said at least one port being both in UG status and selected by STP as a designated port.

17. The method as in claim 16, further comprising:

running Uplinkguard enabled process, and said Uplinkguard enabled process determining whether or not a port set to UG status has been transitioned to forwarding status; and

,

setting said at least one port into blocked state in response to said at least one port being both in UG enabled status and transitioned into forwarding status, and said at least one port not being a root port when in forwarding status.

18. The method as in claim 16, further comprising:

storing a data structure stored in memory, said data structure having entries, said entries having a “

state”

field and a “

role”

field, said state field having the value of “

blocked”

or the value of “

forwarding”

;

providing a first entry having the role field set to “

root port” and

the state field set to forwarding;

providing a second entry having the role field set to “

designated port” and

the state field set to forwarding;

providing a third entry having the role field set to “

blocked port”

and the state field set to blocked; and

,

providing a fourth entry having the role field set to “

uplinkguard enabled” and

the state field set to blocked.

19. The method as in claim 16, further comprising:

not setting said at least one port into a blocked status if said at least one port is selected by STP as a root port.

20. The method as in claim 16, further comprising:

removing said at least one port from a list of ports examined by STP if said port is in the blocked state when running STP.

21. A network switch, comprising:

means for setting a status at least one port of a plurality of ports, said status being set to either a status of capable of transmitting to other switches lower in a spanning tree protocol (spanning tree protocol is hereinafter STP), OR being to a status of NOT being able to transmit to other switches lower in the STP (hereinafter referred to as uplinkguard enabled status, or UG status);

means for setting said at least one port to UG status;

means for running the spanning tree protocol (STP) in said network switch, said STP capable of selecting said at least one port as either a designated port or as a root port;

means for running an uplinkguard enabled process, and said unlinkguard enabled process determining whether or not a port set to UG status has been selected by STP as a designated port; and

,

means for setting said at least one port into blocked state in response to said at least one port being both in UG status and selected by STP as a designated port.

22. The network switch as in claim 21, further comprising:

means for running Uplinkguard enabled process, and said Uplinkguard enabled process determining whether or not a port set to UG status has been transitioned to forwarding status; and

,

means for setting said at least one port into blocked state in response to said at least one port being both in UG enabled status and transitioned into forwarding status, and said at least one port not being a root port when in forwarding status.

23. The network switch as in claim 21, further comprising:

means for storing a data structure stored in memory, said data structure having entries, said entries having a “

state”

field, said state field having the value of “

blocked”

or the value of “

forwarding”

;

means for providing a first entry having the role field set to “

root port” and

the state field set to forwarding;

means for providing a second entry having the role field set to “

designated port”

and the state field set to forwarding;

means for providing a third entry having the role field set to “

blocked port” and

the state field set to blocked; and

,

means for providing a fourth entry having the role field set to “

uplinkguard enabled” and

the state field set to blocked.

24. The network switch as in claim 21, further comprising:

mean for not setting said at least one port into a blocked status if said at least one port is selected by STP as a root port.

25. The network switch as in claim 21, further comprising:

means for removing said at least one port from a list of ports examined by STP if said port is in the blocked state when running STP.

26. A computer readable media, comprising:

said computer readable media having instructions written thereon for execution on a processor for the practice of the method having,

setting a status at for at least one port of a plurality of parts, said status being set to either a status of capable of transmitting to other switches lower in a spanning tree protocol (spanning tree protocol is hereinafter STP), OR being set to a status of NOT being able to transmit to other switches lower in the STP (hereinafter referred to as uplink guard enabled status, or UG status);

setting said at least one port to UG status;

running the spanning tree protocol (STP) in said network switch, said STP capable of selecting said at least one port as either a designated port or as a root port;

running an uplinkguarg enabled process, and said uplinkguard enabled process determining whether or not a port set to UG status has been selected by STP as a designated port; and

,

setting said at least one port into blocked state in response to said at least one port being both in UG status and selected by STP as a designated port.

27. A method for operating a network switch, comprising:

enabling a status of a selected port of the switch to upguard enabled status (hereinafter UG status), the UG status preventing the port from transmitting to a switch lower in a spanning tree established by executing a spanning tree protocol (hereinafter STP), the spanning tree protocol capable of selecting a root port to communicate to a switch upstream in the spanning tree and capable of selecting a designated port to communicate downstream to a switch lower in the spanning tree;

executing the spanning tree protocol (STP), and the STP selecting the selected port as a designated port; and

setting the selected port into blocked state in response to the at least one port being both in UG status and selected by STP as a designated port, the blocked state preventing the selected port from transmitting to a switch lower in the spanning tree.

28. The method of claim 27 further comprising:

removing the selected port from a list of ports examined by STP.

29. A network switch, comprising:

means for enabling a status of a selected port of the switch to upguard enabled status (hereinafter UG status), the UG status preventing the port from transmitting to a switch lower in a spanning tree establised by executing a spanning tree protocol (hereinafter STP), the spanning tree protocol capable of selecting a root port to communicate to a switch upstream in the spanning tree and capable of selecting a designated port to communicate downstream to a switch lower in the spanning tree;

means for executing the spanning tree protocol (STP), and the STP selecting the selected port as a designated port; and

means for setting the selected port into blocked state in response to the at least one port being both in UG status and selected port from transmitting to a switch lower in the spanning tree.

30. The method of claim 29 further comprising:

means for removing the selected port from a list of ports examined by STP.

31. A network switch, comprising:

a first circuit to enable a status of a selected port of the switch to upguard enabled status (hereinafter UG status), the UG status preventing the port from transmitting to a switch lower in a spanning tree established by executing a spanning tree protocol (hereinafter UG status), the UG status preventing the port from transimtting to a switch lower in a spanning tree established by executing a spanning tree protocol (hereinafter STP), the spanning tree protocol capable of selecting a root port to communicate to a swithc upstream in the spanning tree and capable of selecting a designated port to communicate downstream to a switch lower in the spanning tree;

a second circuit to execute the spanning tree protocol (STP), and the STP selecting the selected port as a designated port; and

a third circuit to set the selected port into blocked state in response to the at least one port being both in UG status and selected by STP as a designated port, the blocked state preventing the selected port from transmitting to a switch lower in the spanning tree.

32. The method of claim 31, further comprising:

the first circuit to remove the selected port from a list of ports examined by STP.