S-Series Neighboring SFP+ Ports may Bounce Link when a Transceiver is Inserted or Removed

FAQ_User — Wed, 20 Nov 2013 03:09:00 GMT

Article ID: 12973

Products
S-Series, all firmware

Changes
With firmware 7.03.06.0004 and lower:
Inserted a 1-gigabit (MGBIC) transceiver into a SFP+ port; -or-
Removed a 1-gigabit (MGBIC) transceiver from a SFP+ port.

With firmware 7.11.01.0026 and higher:
Inserted a 1-gigabit (MGBIC) transceiver into a SFP+ port for the first time; -or-
Inserted a 1-gigabit (MGBIC) transceiver into a SFP+ port after a 10-gigabit (10GBASE) transceiver; -or-
Inserted a 10-gigabit (10GBASE) transceiver into a SFP+ port after a 1-gigabit (MGBIC) transceiver.

Symptoms
The link state of some neighboring operational SFP+ ports briefly "bounces".

Cause
Upon system boot, an empty SFP+ port is initially in SFP+(10G) mode.

With firmware 7.03.06.0004 and lower:
Operating an inserted MGBIC requires changing the associated MAC chip from SFP+(10G) mode to SFP(1G) mode for that port, and removing a previously inserted MGBIC returns the associated MAC chip from SFP(1G) mode to SFP+(10G) mode for that port.

With firmware 7.11.01.0026 and higher:
The MAC chip is reset only as necessary to accommodate the needs of an inserted MGBIC or 10GBASE transceiver.

In any case, the group of ports sharing that MAC chip will be reset and restarted. The reset/restart operational outage lasts roughly 2-3 seconds and is signaled to the switching protocols as port down/port up.

Release notes (for example, version 7.03.03.0001) state, in the 'Known Restrictions and Limitations' section:
SFP+ Port Speed
When an SFP (1G) module is inserted or removed from an SFP+ (10G capable) port, all ports on the associated MAC chip are reset. This results in a momentary loss of link and traffic on affected ports and forces topology protocols to process a link bounce. On SSA all 10G ports are in the same group. All ports on a 10G Option Module are grouped together. For S blades shipping with factory configured ports the groups are: tg.x.1-4, tg.x.5-8, tg.x.9-12, tg.x.13-16.

Solution
Functions as Designed (FAD).

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S-Series Neighboring SFP+ Ports may Bounce Link when a Transceiver is Inserted or Removed