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Nexus 5000 Tips for Catalyst Admins

I kind of understand the pain that each network admin has when changing the platform, especially if you haven’t had enough time to get experience on the new system prior to production. This article is meant to help the Cisco Catalyst admins to get some hold of Nexus 5000 series switch. Don’t expect this to give you a detailed list of the platform differences however, these are just scratching the surface.

In Catalyst you used “sh log” command to show the log, obviously. In Nexus the command shows you much more and thus takes longer time to get you the log output. Use “sh log log” (sh logging logfile) instead.

Also, to get the latest log lines you can use the “sh log last 40” command to get the last 40 (or whatever you want) lines of log output. Nice and handy, no need to use any filtering with “begin/end/include” commands to check the results of your changes. Btw, the filtering commands have been extended a lot, too, check them out!

N5k-1# sh log | ?
  cut      Print selected parts of lines.
  diff     Show difference between current and previous invocation (creates
temp files: remove them with 'diff-clean' command and dont use it on
commands with big outputs, like 'show tech'!)
  egrep    Egrep - print lines matching a pattern
  grep     Grep - print lines matching a pattern
  head     Display first lines
  human    Output in human format
  last     Display last lines
  less     Filter for paging
  no-more  Turn-off pagination for command output
  section  Show lines that include the pattern as well as the subsequent
lines that are more indented than matching line
  sort     Stream Sorter
  tr       Translate, squeeze, and/or delete characters
  uniq     Discard all but one of successive identical lines
  wc       Count words, lines, characters
  xml      Output in xml format (according to .xsd definitions)
  begin    Begin with the line that matches
  count    Count number of lines
  end      End with the line that matches
  exclude  Exclude lines that match
  include  Include lines that match

FEXes (Fabric Extenders) are clearly a new element for Catalyst admins. “sh fex” gets you the list of connected FEXes, and “sh fex xxx” shows basics of the connected FEX:

N5k-1# sh fex 141
FEX: 141 Description: sw01-fex141   state: Online
  FEX version: 5.1(3)N1(1) [Switch version: 5.1(3)N1(1)]
  Extender Serial: <serial number>
  Extender Model: N2K-C2248TP-1GE,  Part No: 73-13232-01
  Pinning-mode: static    Max-links: 1
  Fabric port for control traffic: Eth1/29
  FCoE Admin: false
  FCoE Oper: true
  FCoE FEX AA Configured: false
  Fabric interface state:
    Eth1/29 - Interface Up. State: Active

It shows the fabric interface of the Nexus 5000 (the port where the “uplink” of the FEX is connected, the FEX uplinks are called fabric interfaces), for example.

Btw, don’t touch the “pinning max-links” command unless you really understand what you are doing! Check the docs, docs.

“sh fex xxx detail” obviously shows you even more information, and “sh fex xxx transceiver” shows you which kind of optics/copper you have on the FEX because the normal “sh int status”/”sh int transceiver” switch commands don’t show the fabric ports at the FEX end.

If and when you are using vPC you need to use the “sh vpc” command variants to verify that your vPC configurations are working as you expected. For example, “sh vpc brief” shows if you have any consistency problems with your vPCs. In case of problems you need to use “sh vpc consistency-parameters vpc xxx” to show more information.

What else would you recommend to Nexus newbies?

Cisco Nexus 5000 Series documentation is found here:


Add a Comment
  1. Markku, this is a great site. Glad to see all the Nexus content.

    If you are running FEX’s in a dual-homed active/active setup use “sh run include-switch-profile” to show the separation between the standard config and what was entered in your config sync switch profile. I even modified rancid to backup my configs this way.

    1. HI Markku, A bit off topic, did you use the cisco-xr profile to get the config from your N5k? I am struggling to get Rancid configured with Nexus.

  2. Minimal, that’s a good point. The configuration entered in switch profile is shown in normal “sh run” output but “sh run include-switch-profile” or even “sh run switch-profile” helps to identify the configuration applied with the switch profile. Thanks!

  3. sh run int all
    Shows all config, including Nexus defaults.

    sh int status fex 10x – nice way to narrow down sh int status to a single fex

    when using ping or while ftp/tftp, using vrf’s (management) ping vrf management

    sh install all impact kickstart system – good way to see what impact new IOS brings.
    I agree “sh vpc consistency-parameters vpc xxx” -this is a great command to know, when you are wondering why your vlan/vpc arent working.

  4. Thanks Ron!

  5. Good hints from Ian as well (above)!

    One of the biggest hints is this: 😎

    You can use the exec mode commands (like show int status) anywhere, you don’t have to use the “do” command (where the question mark doesn’t work in IOS) or exit from the configuration mode anymore!

  6. show etherchannel summary has been replaced by show port-channel summary.

    You no longer need the “range” keyword to specify a range of interfaces (it will actually reject the “range” keyword)

  7. I was searching the Internet for information on QoS and came across your site. I am connecting a 3750X directly to a Nexus 5548. Is QoS between these two different switches possible? I have configured simple interface QoS (not system qos) and it does not seem to work. Can you recommend a source of information on this topic?
    Thank you

    1. Oops, old message but I’m going to reply anyway. QoS is “always” possible because it is handled independently hop by hop. You need to decide if you are going to mark the frames somehow and then trust the markings on the next switch(es), or do you just inspect the frames again at each switch. Configuring QoS is such a wide topic that I’m not going to go there here 😀 Nexus 5000 series does not have the best QoS features anyway.

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