Showing results for 
Search instead for 
Did you mean: 

Community Manager

Ask the Expert: Troubleshooting Nexus 5000/2000 series switches

Read the bioWith Prashanth Krishnappa

Welcome to the Cisco Support Community Ask the Expert conversation. This is an opportunity to learn about how to troubleshoot the Nexus 5000/2000 series switches.


Prashanth Krishnappa is an escalation engineer for datacenter switching at the Cisco Technical Assistance Center in Research Triangle Park, North Carolina. His current responsibilities include escalations in which he troubleshoots complex issues related to the Cisco Catalyst, Nexus and MDS product lines as well as providing training and author documentation. He joined Cisco in 2000 as an engineer in the Technical Assistance Center. He holds a bachelor's degree in electronics and communication engineering from Bangalore University, India, and a master's degree in electrical engineering from Wichita State University, Kansas. He also holds CCIE certification (#18057).

Remember to use the rating system to let Prashanth know if you have received an adequate response. 

Prashanth might not be able to answer each question due to the volume expected during this event. Remember that you can continue the conversation on the Data Center sub-community discussion forum shortly after the event. This event lasts through June 29, 2012. Visit this forum often to view responses to your questions and the questions of other community members.


Thanks Leo and Prashanth


Leo Laohoo
VIP Community Legend

Thanks Sid.

I just completed Nexus training so I'm eager to learn from the experts here. 

Good responses Prashanth. 

Dennis Goh


Since we are in this topic, are we able to turn "on" or "off" the L3 capabilities of the N5548UPs?


Dennis Goh

Hello Dennis

Most of the features including L3 features are enabled using the feature command. Here is an output from a lab switch

5548-1(config)# feature ?

  bgp             Enable/Disable Border Gateway Protocol (BGP)

  cts             Enable/Disable CTS

  dhcp            Enable/Disable DHCP Snooping

  dot1x           Enable/Disable dot1x

  eigrp           Enable/Disable Enhanced Interior Gateway Routing Protocol (EIGRP)

  fcoe            Enable/Disable FCoE/FC feature

  fcoe-npv        Enable/Disable FCoE NPV feature

  fex             Enable/Disable FEX

  flexlink        Enable/Disable Flexlink

  hsrp            Enable/Disable Hot Standby Router Protocol (HSRP)

  http-server     Enable/Disable http-server

  interface-vlan  Enable/Disable interface vlan

  lacp            Enable/Disable LACP

  msdp            Enable/Disable Multicast Source Discovery Protocol (MSDP)

  npiv            Nx port Id Virtualization (NPIV) feature enable

  npv             Enable/Disable FC N_port Virtualizer

  ospf            Enable/Disable Open Shortest Path First Protocol (OSPF)

  pim             Enable/Disable Protocol Independent Multicast (PIM)

  port-security   Enable/Disable port-security

  private-vlan    Enable/Disable private-vlan

  privilege       Enable/Disable IOS type privilege level support

  rip             Enable/Disable Routing Information Protocol (RIP)

  ssh             Enable/Disable ssh

  tacacs+         Enable/Disable tacacs+

  telnet          Enable/Disable telnet

  udld            Enable/Disable UDLD

  vpc             Enable/Disable VPC (Virtual Port Channel)

  vrrp            Enable/Disable Virtual Router Redundancy Protocol (VRRP)

  vtp             Enable/Disable Vlan Trunking Protocol (VTP)

So if a feature is not needed, you can turn it off using "no feature".



Hi Prashanth,

Thank you for your reply. Does that mean that if I do not turn on any L3 features on the Nexus 5500, I can be able to scale up to 24 FEXs dual-homed?

P.s. yup, I have L3 daughterboard installed

Hi Dennis

The switch is considered Layer 3 only when you install the L3 licenses. So if you do not need the L3 features at this time and want to use it as L2 switch with upto 24 FEX, you could uninstall all the L3 licenses.



Hi Prashanth,

Correct me if I'm wrong, What I do to be able to scale up to 24 FEXs is by backing up my licenses, then uninstalling the L3 license. And if one day in the future I need this L3 feature, I just restore my license from the backup that I've made?

Btw, how do I restore backed up licenses on the N5500? I can't seem to find any guides on it.

Thanks in advance.

Hello Dennis

Just installing license using "clear license" command should be enough. Here is an example from my lab switch.

5548-1# clear license ?




  WORD                      License file to be uninstalled

But if you want to back up all the license files, you can do that too. Here is how you do it.

1)copy license bootflash:file-name.tar

2)Then issue "clear license" like above.

If you need to, reinstall the license at some point in the future

1)tar extract bootflash:file-name.tar

2)Install the license back using "install license bootflash:" command.

Hi Prashanth,

Question about Enhanced vPC-

"The Dual-homed FEX topology can also be deployed for servers that have multiple NICs

but do not support 802.3ad"

Does the above statement mean we can't use LACP to dual home a server to dual homed FEXs?




here is one simple question: if I have Nexus 5k connected to another cisco device that also supports vPC, will CDP work if port on one side belongs to vPC while on another side is configured as simple access port?




Is there any Nexus Switch Emulator/Manager available which can be used for getting switch statistics?

Is there any Nexus Switch Emulator/Manager available which can be used for getting switch statistics?

not sure but try DCNS.

Hi Dennis,

I'm curently facing a similar problem. Do you het an answer or solve this issue?

The Cisco answer is diabling Layer 3 features but do we need to rmove the license and / or the Layer 3 card?



Hello Pascal,

Newer versions of NX-OS supports up to 16 EvPCs (my customer uses 10 FEXs so far) hence I did not attempt to try out removing the licenses. I have yet to try removing the license as my project timeline grew shorter and I was unable to test anymore. If you have the time, do give Prashant's guides a try and let us know If I have a chance to deal with N55XX with L3 module, I will attempt to try this out


Dennis Goh

Dennis Goh

Is this post still active?

Would like to ask further on L3 modules. Lets say I'm performing an NX-OS upgrade on a Nexus5500 series which is equipped with L3 module. I have L3 license installed, however I do not use any L3 capabilities at all.

Whenever I perform an ISSU check for upgrading, the output will always be "disruptive" which I suspect is due to the reason that I have an L3 module installed. I know for a fact that my configurations on a Nexus5500 unit without an L3 module will be non-disruptive. Can I safely tell the customer that their production network will not encounter any downtime if I perform an NX-OS upgrade?

Thanks in advance!

Dennis Goh

Content for Community-Ad