Loop prevention system and method in a stackable ethernet switch system

1. A loop prevention method operable in a stackable Ethernet switch system (SESS) having at least two stackable switch elements, wherein each switch element includes at least one stacking port and at least one core switch port such that said at least one core switch port is operable to be connected to a core switch, said loop prevention method comprising:

monitoring control management traffic on said at least one stacking port of each of said stackable switch elements;

upon determining that there is a loss of said control management traffic on a stacking port of a particular switch element of said SESS, disabling user data traffic on said stacking port of said particular switch element while continuing to keep a control/management traffic path open to avert a loop condition involving said user data traffic in said SESS; and

enabling said user data traffic on said stacking port of said particular switch element upon detecting that said control management traffic on said stacking port has resumed.

2. The loop prevention method as recited in claim 1 , wherein said loss of said control management traffic on said stacking port of said particular switch element is determined based on detecting that “Keep Alive” messages from a neighboring switch element connected to said particular switch element are not received after a period of time.

3. The loop prevention method as recited in claim 2 , wherein said period of time is predetermined.

4. The loop prevention method as recited in claim 2 , wherein said period of time is configurably variable.

5. The loop prevention method as recited in claim 1 , wherein said monitoring is performed after initial configuration of said SESS in which at least one of said core switch ports is rendered into a blocking state upon coupling to said core switch.

6. The loop prevention method as recited in claim 1 , wherein said control management traffic is monitored on each of said stackable switch elements by a stacking port traffic logic block associated with each stackable switch element.

7. A loop prevention apparatus operable in a stackable Ethernet switch system (SESS) having at least two stackable switch elements, wherein each switch element includes at least one stacking port and at least one core switch port such that said at least one core switch port is operable to be connected to a core switch, said loop prevention apparatus comprising:

means for monitoring control management traffic on said at least one stacking port of each of said stackable switch elements;

means, operable responsive to determining that there is a loss of said control management traffic on a stacking port of a particular switch element of said SESS, for disabling user data traffic on said stacking port of said particular switch element while continuing to keep a control/management traffic path open to avert a loop condition involving said user data traffic in said SESS; and

means for enabling said user data traffic on said stacking port of said particular switch element upon detecting that said control management traffic on said stacking port has resumed.

8. The loop prevention apparatus as recited in claim 7 , wherein said loss of said control management traffic on said stacking port of said particular switch element is determined based on detecting that “Keep Alive” messages from a neighboring switch element connected to said particular switch element are not received after a period of time.

9. The loop prevention apparatus as recited in claim 8 , wherein said period of time is predetermined.

10. The loop prevention apparatus as recited in claim 8 , wherein said period of time is configurably variable.

11. The loop prevention apparatus as recited in claim 8 , wherein said means for monitoring said control management traffic is operable after initial configuration of said SESS in which at least one of said core switch ports is rendered into a blocking state upon coupling to said core switch.

12. A stackable Ethernet switch system (SESS), comprising:

at least two stackable switch elements, wherein each switch element includes at least one stacking port and at least one core switch port such that said at least one core switch port is operable to be connected to a core switch;

logic implemented with each stackable switch element for monitoring control management traffic on said at least one stacking port of each of said stackable switch elements;

logic implemented with each stackable switch element, operable responsive to determining that there is a loss of said control management traffic on a stacking port of a particular switch element of said SESS, for disabling user data traffic on said stacking port of said particular switch element while continuing to keep a control/management traffic path open to avert a loop condition involving said user data traffic in said SESS; and

logic implemented with each stackable switch element for enabling said user data traffic on said stacking port of said particular switch element upon detecting that said control management traffic on said stacking port has resumed;

wherein the logic comprises at least one of a computer-readable medium, hardware, or firmware of each stackable switch element.

13. The stackable Ethernet switch system as recited in claim 12 , wherein said loss of said control management traffic on said stacking port of said particular switch element is determined based on detecting that “Keep Alive” messages from a neighboring switch element connected to said particular switch element are not received after a period of time.

14. The stackable Ethernet switch system as recited in claim 13 , wherein said period of time is predetermined.

15. The stackable Ethernet switch system as recited in claim 13 , wherein said period of time is configurably variable.

16. The stackable Ethernet switch system as recited in claim 12 , wherein said logic for monitoring said control management traffic is operable after initial configuration of said SESS in which at least one of said core switch ports is rendered into a blocking state upon coupling to said core switch.

17. The stackable Ethernet switch system as recited in claim 12 , wherein said stackable switch elements are arranged in a star configuration.

18. The stackable Ethernet switch system as recited in claim 12 , wherein said stackable switch elements are arranged in a ring configuration.

19. The stackable Ethernet switch system as recited in claim 12 , wherein said stackable switch elements are arranged in a chain configuration.