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Ask the Expert: Basic Introduction and Troubleshooting on Cisco Nexus 7000 NX-OS Virtual Device Context

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Jan 2nd, 2013

Vignesh R. PWith Vignesh R. P.

Welcome to the Cisco Support Community Ask the Expert conversation.This is an opportunity to learn and ask questions of Cisco expert Vignesh R. P. about the Cisco® Nexus 7000 Series Switches and support for the Cisco NX-OS Software platform .

The Cisco® Nexus 7000 Series Switches introduce support for the Cisco NX-OS Software platform, a new class of operating system designed for data centers. Based on the Cisco MDS 9000 SAN-OS platform, Cisco NX-OS introduces support for virtual device contexts (VDCs), which allows the switches to be virtualized at the device level. Each configured VDC presents itself as a unique device to connected users within the framework of that physical switch. The VDC runs as a separate logical entity within the switch, maintaining its own unique set of running software processes, having its own configuration, and being managed by a separate administrator.

Vignesh R. P. is a customer support engineer in the Cisco High Touch Technical Support center in Bangalore, India, supporting Cisco's major service provider customers in routing and MPLS technologies. His areas of expertise include routing, switching, and MPLS. Previously at Cisco he worked as a network consulting engineer for enterprise customers. He has been in the networking industry for 8 years and holds CCIE certification in the Routing & Switching and Service Provider tracks.

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

Vignesh 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 through January 18, 2013. Visit this forum often to view responses to your questions and the questions of other community members.

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tenaro.gusatu.novici Sun, 01/06/2013 - 15:03

Hi Vignesh,

I would like to learn a bit more about VDC feature (and do some hands-on testing) but I don't have access to Nexus 7k. Any chance this feature will be available on Nexus 5k soon? Or maybe on 1000V? I hope my question is not out of the scope for this session.

Cheers,

Tenaro

virajend Mon, 01/07/2013 - 06:09

Hi Tenaro,

A Nexus 5K has the default VDC alone. You cannot create further VDCs.And as far is I know the VDC feature is not available in Nexus 1000V also and I dont think that it is getting introduced in the near future too.So I am afraid that you would need a Nexus 7K to get some practice on the VDC feature. Kindly do revert in case of further clarifications.

Thanks & Regards,

Vignesh R P

r.dabbous Mon, 01/14/2013 - 01:31

Hi Vignesh

Is there is any limitation to connect a N2K directly to the N7K?

if i have a an F2 card 10G and another F2 card 1G and i want to creat 3 VDC'S

VDC1=DC-Core

VDC2=Aggregation

VDC3=Campus core

do we need to add a link between the different VDC's

thanks

virajend Mon, 01/14/2013 - 07:37

Hello,

You can extend the Cisco Nexus 7000 Series switch architecture by connecting up to 32 FEXs(N2Ks) as remote I/O modules. Depending on which FEX(N2K) model that you connect to the switch, the FEX(N2K) provides top-of-the-rack connectivity for up to 48, 32, or 24 hosts, and it becomes an extension of the parent Cisco Nexus 7000 Series switch fabric, with the FEX(N2K) and the switch becoming a virtual modular system. The FEX(N2K) forwards all 100/1000 Ethernet or 1- and 10-Gigabit Ethernet traffic from the hosts to the switch over 10-Gbps uplinks. Traffic flows from the switch to the FEX(N2K) over the 10-Gbps uplinks and to the individual hosts over 100/1000 Ethernet or 1- and 10-Gigabit Ethernet downlinks.

For more details take a look at the below link.

http://www.cisco.com/en/US/docs/switches/datacenter/nexus2000/hw/installation/guide/overviewN7K.html

Kindly revert incase of further assistance.

With respect to the second question regarding VDCs, I would like to know if you are planning to have inter communication between the three VDCs.

Thanks & Regards,

Vignesh R P

r.dabbous Tue, 01/15/2013 - 01:25

hi Vignesh thanks alot for your support regarding the 2nd question we require the different VDC's to communicate together

and if the link between the VDC's is 1G is there is any issue in it since that most of the links are 10G and the link

tenaro.gusatu.novici Mon, 01/14/2013 - 10:34

Me again,

first of all, thanks a lot for very detailed answer!

What will be your favourite troubleshooting command(s) when talking about VDC feature? I know,  there are many documents describing this feature and they contain various commands. I also know, from experience, that outputs for debug commands are normally not described at all (if memory serves me well, last time Cisco published this was for IOS version 11.2). As an expert for VDC, you have your favourite troubleshooting procedures and I'm sure you can pick one/two/three command(s) and explain to us which parameters in particular we should look for in the outputs, what do they mean and why it is important (i.e. what most common problems can be spotted).

Thanks again,

Tenaro

virajend Mon, 01/14/2013 - 23:02

Hello Tenaro,

The below mentioned are the basic stuffs that you need to check while trouble shooting VDC related issues. If you are looking for trouble shooting commands to address some specific VDC related issue that you have come across, kindly let me know so that I can assist you further.

Basic Checklist
==================

Verify that you are logged into the device as network-admin if you are creating or modifying VDCs.

Verify that you are in the 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 VDCs.


Following commands help to display VDC information:
======================================================

* show vdc membership - Displays information about which interfaces are assigned to a VDC.
* show vdc resource - Displays information about the resources assigned (Command is available only in the default VDC).
* show vdc current-vdc - Displays the VDC you are currently in.


Common VDC related issues
============================


1) You cannot create a VDC.

Possible Cause: You are not logged in as network-admin.

Solution- Log into the device with an account that has network-admin privileges.

Possible Cause: You are not logged into the default VDC.

Solution- Use the switchto command to switch to the default VDC to allocate resources.

Possible Cause: There are not enough resources.

Solution- Use the show vdc resources [detail] or show vdc resource template command to determine your available resources. Modify your template or create a VDC with fewer resources by using the limit-resource  command in VDC configuration mode.


2) You cannot log into a device.

Possible Cause: There is no account information for the VDC.

Solution- Log into the device as network-admin and use the switchto command to switch to the VDC and configure the password and network connectivity for this VDC.

Possible Cause: You are using an incorrect VDC username.

Solution- Log into the device with the account created for that VDC.


3) You Cannot Switch to a VDC.

Possible Cause: You are not logged in as network-admin.

Solution- Log into the device with an account that has the correct privileges.


4) You cannot allocate an interface to a VDC.

POssible Cause: You are not logged in as network-admin.

Solution- Log into the device with an account that has the correct privileges.

Possible Cause: You are not logged into the correct VDC.

Solution- Use the switchto command to switch to the default VDC to allocate resources.

Possible Cause: The interface is part of a dedicated port group.

Solution- Use the show interface capabilities  command to determine if the port is dedicated. All ports in a dedicated port group must be in the same VDC.

Possible Cause: The interface is on the Cisco Nexus 7000 Series 32-port 10-Gbps Ethernet module (N7K-M132XP-12).

Solution- You must allocate all ports in a port group to the same VDC for this specific module.

r.dabbous Tue, 01/15/2013 - 01:59

hi Vignesh thanks alot for your support regarding the 2nd question we require the different VDC's to communicate together

and if the link between the VDC's is 1G is there is any issue in it since that most of the links are 10G and the link

virajend Thu, 01/17/2013 - 05:31

Hello Raed,

Each VDC is its own switch. They have their own processes, VLANs, routing protocols, spanning-tree, management plane, and configuration. It's really a completely separate switch. Interfaces are assigned to the VDC to provide external connectivity. Inter-VDC communication is only via external interfaces, there is no internal switch like in VMware.

So if you are planning to have inter communication between the three VDCs, then you need to add a link between the different VDC's.


Are you planning to have 1G interfaces of a LC to be a part of different VDCs & these 1G interfaces would be used for inter VDC communication, whereas the external facing interfaces on all these VDCs would be of 10 G capacity? Kindly clarify.

Thanks & Regards,

Vignesh R P

vann_will Tue, 01/15/2013 - 14:51

Hello

I was hoping maybe you answer this for me, If I setup a vpc between my core 5596 and my dsw 5548 with all the svi's created on the 5596. Should I be able to ping my svi's that I created on the 5596 from inside the 5548's? If so what must be configured to do so?

Thank you in advance

virajend Wed, 01/16/2013 - 02:20

Hello,

I am extremely sorry to say that vPC is out of scope with respect to this thread. This thread deals with VDC on N7K.

Thanks a lot for understanding.

Best Regards,

Vignesh R P

jimplum06 Thu, 01/17/2013 - 00:57

Hi There

We are trying to change the ntp settings on our pair of nexus7000's. These were wrongly configured on installation. We wish to point the ntp to the DC's. However we are unable to change the settings

Jim

virajend Fri, 01/18/2013 - 06:55

Hi Jim,

I would encourage you to share the configurations from the device, for me to comment further on this.

Thanks & Regards,

Vignesh R P

Andras Dosztal Thu, 01/17/2013 - 01:34

Hello Vignesh,

Using Sup1, do I need the Advanced LAN Enterprise License to have an admin VDC plus one VDC for data traffic?

Thank you in advance.

virajend Fri, 01/18/2013 - 06:54

Hello Andras,

You would need the Cisco NX-OS Advanced LAN License.

Thanks & Regards,

Vignesh R P

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