Troubleshooting Cisco Nexus 7000 Series Switches

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Cisco Nexus 3000 Series NX-OS

Modular QoS CLI

The Cisco Modular QoS CLI (MQC) provides a standard set of commands for configuring QoS.

You can use MQC to define additional traffic classes and to configure QoS policies for the whole system and for individual interfaces. Configuring a QoS policy with MQC consists of the following steps:

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CCNP Switch bonus – Troubleshooting Ethernet

Troubleshooting Ethernet

Interface Commands (show interfaces – show interfaces vg-anylan)

Cisco NX-OS/IOS Interface Comparison

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Differences between IOS and IOS XE

Differences between IOS and IOS XE

Cisco IOS:

  • IOS is monolithic, completely adherent to the hardware, and does not provide any kind of isolation between “processes”, neither from a CPU nor memory point of view.
  • Virtual memory is shared by all IOS processes: nothing prevents buffer overflows.
  • Scheduler is non-preemptive: if SNMP decides it should keep CPU busy, it can, and other processes (BGP…) will be prevented from running.
  • You cannot upgrade IOS (or parts of it) without disruption unless you are running expensive dual-supervisor hardware.

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Cut-through, corruption and CRC-stomping

Corrupted frames are the devils spawn.  A few noisy links causing frame corruption can quickly degrade network performance, and troubleshooting them is getting harder.  These integrity errors generally occur when signal noise causes a binary ‘1’ to be mistaken for a binary ‘0’ or vice-versa.  This post takes a look at integrity errors and the impacts of corrupted frames in a cut-through switched network.  Throughout this post I’ll use the term ‘CRC errors’ term to refer to frame integrity errors which were detected by CRC comparison.

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RIB (or routing table) and FIB (or forwarding table) are two different tables within an IP networking platform.  They share common information but perform two distinctly different purposes.  They also each have a different degree of resource capacity to perform their respective roles.

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