Cisco 350 Series Administration Manual page 154

Administration: Stack Management
Stack Ports
Cisco 350, 350X and 550X Series Managed Switches, Firmware Release 2.4, ver 0.4
Stack Port States
Stack ports can be in one of the following states:
• Down—Port operational status is down or stack port operational status is up, but traffic
cannot pass on the port.
• Active—Stack port was added to a stack LAG whose stack port operational status is up
and traffic can pass on the port and it is a member of a stack LAG.
• Standby—Stack port operational status is up and bidirectional traffic can pass on the
port, but the port cannot be added to a stack LAG, and the port does not transmit traffic.
Possible reasons for a port being in standby are:
- Stack ports with different speeds are used to connect a single neighbor.
- On the Sx550X/SG350, more than two interfaces or an unsupported interface
combination is used to connect to a single neighbor
Physical Constraints for Stack LAGs
The following factors constrain the use of stack LAGs:
• A stack LAG must contain ports of the same speed.
• When attempting to connect a unit to a stack whose topology is not a ring/chain (for
example, trying to connect a unit to more than two neighboring units - star topology),
only two stack LAGs can be active, the remainder of the stack ports are set to standby
mode (inactive).
Default Stack and Network Ports
All ports are configured as network ports by default.
Auto Selection of Port Speed
The stacking cable type is discovered automatically when the cable is connected to the port
(auto-discovery is the default setting). The system automatically identifies the stack cable type
and selects the highest speed supported by the cable and the port.
A SYSLOG message (informational level) is displayed when the cable type is not recognized.
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