Reference Guide

NOTE: When you split a 40G port (such as fo 0/4) into four 10G ports, the 40G interface
configuration is available in the startup configuration when you save the running configuration by
using the write memory command. When a reload of the system occurs, the 40G interface
configuration is not applicable because the 40G ports are split into four 10G ports after the reload
operation. While the reload is in progress, you might see error messages when the configuration file
is being loaded. You can ignore these error messages. Similarly, such error messages are displayed
during a reload after you configure the four individual 10G ports to be stacked as a single 40G port.
To split a single 40G port into four 10G ports, use the following command.
• Split a single 40G port into 4-10G ports.
CONFIGURATION mode
stack-unit stack-unit port number portmode quad
– stack-unit: enter the stack member unit identifier of the stack member to reset. The range is
from 0 to 11.
– number: enter the port number of the 40G port to be split. The range is from 0 to 47 for 10G ports
and 48, 52, 56 and 60 for 40G ports.
Important Points to Remember
• Splitting a 40G port into four 10G ports is supported on standalone and stacked units.
• You cannot use split ports as stack-link to stack a S4820T system.
• The unit number with the split ports must be the default (stack-unit 0).
To verify port splitting, use the show system brief command. If the unit ID is different than 0, it must
be renumbered to 0 before ports are split by using the
stackunit id renumber 0 command in EXEC
mode.
• The quad port must be in a default configuration before you can split it into 4x10G ports. The 40G
port is lost in the configuration when the port is split; be sure that the port is also removed from other
L2/L3 feature configurations.
• The system must be reloaded after issuing the CLI for the change to take effect.
Link Dampening
Interface state changes occur when interfaces are administratively brought up or down or if an interface
state changes.
Every time an interface changes a state or flaps, routing protocols are notified of the status of the routes
that are affected by the change in state. These protocols go through the momentous task of re-
converging. Flapping; therefore, puts the status of entire network at risk of transient loops and black
holes.
Link dampening minimizes the risk created by flapping by imposing a penalty for each interface flap and
decaying the penalty exponentially. After the penalty exceeds a certain threshold, the interface is put in an
Error-Disabled state and for all practical purposes of routing, the interface is deemed to be “down.” After
the interface becomes stable and the penalty decays below a certain threshold, the interface comes up
again and the routing protocols re-converge.
Link dampening:
• reduces processing on the CPUs by reducing excessive interface flapping.
Interfaces
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