Troubleshooting Process Nexus 7000

Troubleshooting Nexus 7000 series is not that different then troubleshooting any other datacenter switches. However following a logical step will help us navigate and isolate the issue. Here I will talk about the steps , not the detailed troubleshooting of specific issues.

We can actually break down the issues Nexus switches can have in 4 areas..

  1. Physical Port issues
  2. Physical switch issues
  3. Layer 2 issues
  4. Layer 3 issues

Once we identify the key area of the problem we can then drill down in depth to find where exactly the issue might be coming from .

Have a look at the below chart

troubleshooting-chart

 

 

Troubleshooting Upgrades and Reboots: 

Time to time we might have to do upgrades or reboots for network maintenance. We have to take extra care while doing so on a Nexus 7000 series switch. We should try to minimize the network disruption while performing the upgrades and reboots specially in production environment. We must know how to recover quickly if something goes wrong.

Cisco NX-OS consist of two images. Kickstart image and the system image. These two images should be same version to bring up the system.

We should follow the following check-lists while preparing for upgrades..

troubleshooting-chart 2

Troubleshooting Licensing:

Let’s look at the guidelines for cisco NX-OS licensing..

  1. Do not ignore the grace period.  Allow 60 days before the expiring date to order, ship and install the new licenses. 
  2. Carefully determine what features we should use and what licenses do we need for those features.
  3. Order your license accurately , serial number of the chassis is very important. It must be the same on the  PAK  key. Use show  license host-id  to obtain the chassis serial number.
  4. Always archive /back up the license .
  5. Don’t attempt to use it on another device.

Troubleshooting VDCs on Nexus switches:

  • Verify that you are logged into the device as admin if you are creating or modifying VDCs
  • Verify that you are in correct VDC. You must be in the default VDC to configure VDCs
  • Verify that you have installed the Advanced Services License to configure VDCs.
  • Verify that you are not attempting to create more than three non-default VDCs.

 

Troubleshooting Ports:

  • Check the physical media to ensure there are no damaged parts.
  • Verify the SFP
  • Verify that the port is no shutdown.
  • Do show interface command from CLI to see the state of the port
  • Verify that  you have configured port as a dedicated port, and not connected to any other 3 ports in the port group.

To troubleshoot port channels and trunking issue , we should check the following issues first..

  • show port-channel compatibility-parameters  command to to determine port-channel requirements. This output shows what ports in what condition can be part of a port-channel.
  • Ensure all interface on the port channel have same destination device.
  • Vefify that either side of the port channel is connected to the same number of interfaces
  • Verify that each interface is connected to same type of interface on the other side
  • Verify that all required VLANs on a trunk port are in the allowed VLAN list.

Troubleshooting VLANs: 

  • Verify the physical connectivity for any problem ports or VLANs
  • Verify that you have both end devices in the same VLAN
  • Verify that any private VLAN configuration and associations are correct.

Troubleshooting Spanning Tree Protocol on Nexus 7000: 

Spanning tree protocol works at layer 2 level, to provide a loop free network. Layer 2 LAN ports send and receive STP frames at regular intervals. Network do not forward these frames , but use the frames to construct a loop free path.

Here’s the checklist to troubleshoot STP issues

  • Verify the type of spanning tree configured on all ports in your LAN
  • Verify the network topology including all interconnected ports and switches.
  • Verify the primary and secondary root bridge and any configured Cisco STP extensions.

Troubleshooting Routing : 

Begin troubleshooting routing issues by checking the following issues first..

  • Verify that the routing protocol is enabled
  • Verify that the address family is configured if necessary
  • Verify that you have configured the correct VRF for your routing protocol.

 

I know this is not the whole picture of a troubleshooting, but some logical steps. In each steps we can have so many different scenarios. Hopefully this guideline will help us towards our troubleshooting.

 

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