Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 497

• The QSA module does not have a designated EEPROM. To recognize a QSA, Dell Networking OS reads the EEPROM corresponding to a SFP+ or SFP module that is plugged into QSA. The access location of this EEPROM is different from the EEPROM location of the QSFP+ module. • The diagnostics application is capable of detecting insertion or removal of both the QSA as well as the SFP+ or SFP optical cables plugged into the QSA. In addition, the diagnostic application is also capable of reading the DDS and Vendor information from the EEPROM corresponding to SFP+ or SFP optical cables. As a result, no separate detection of QSA is required. Support for LM4 Optics The newly supported LM4 optics are similar in behavior to the LR4 optics that are already supported. However, in the output of show inventory media command, an LM4 optical module is denoted as 40G-LM4. Barring this exception, the functionality and behavior of LM4 optics is similar to LR4 optics. Example Scenarios Consider the following scenarios: • QSFP port 0 is connected to a QSA with SFP+ optical cables plugged in. • QSFP port 4 is connected to a QSA with SFP optical cables plugged in. • QSFP port 8 in fanned-out mode is plugged in with QSFP optical cables. • QSFP port 12 in 40 G mode is plugged in with QSFP optical cables. 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 reconverging. 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. • improves network stability by penalizing misbehaving interfaces and redirecting traffic. • improves convergence times and stability throughout the network by isolating failures so that disturbances are not propagated. Important Points to Remember • Link dampening is not supported on VLAN interfaces. • Link dampening is disabled when the interface is configured for port monitoring. • You can apply link dampening to Layer 2 and Layer 3 interfaces. • You can configure link dampening on individual interfaces in a LAG. Interfaces 497