Ask the Expert: Cisco Nexus 7000 Series Switches and FabricPath

[Monica Lluis]

This session will provide an opportunity to learn and ask questions about Cisco Nexus 7000 Series Switches and FabricPath technology.

 
Cisco Fabricpath technology on the Nexus 7000 switches introduces new capabilities and design options that allow network operators to create Ethernet fabrics that maximize bandwidth availability, provide design flexibility, and simplify and cost-reduce network and application deployment and operation. Fabricpath leverages many of the best characteristics of traditional Layer 2 and Layer 3 technologies, combining them into a new control-plane and data-plane implementation that combines the plug-and-play deployment model of a bridge Spanning Tree environment with the stability, re-convergence characteristics, and ability to leverage multiple parallel paths typical of a Layer 3 routed environment. The result is a escalable, flexible, and highly-available Ethernet fabric suitable for the most demanding Data Center environments.

Ask questions from Monday, March 7 to March 18, 2016

Featured Experts

Chandan Sarkar is a customer support engineer in High-Touch Technical Services (HTTS). He has over 9 years of experience in the industry working with large enterprises and telecom networks. His areas of expertise include Cisco Catalyst 2000, 3000, 4000, 6500, and Cisco Nexus 7000,Nexus 5000, Nexus 3000, Nexus 2000, UCS, and MDS SAN Switches. Sarkar holds several certifications including CCNP, VPC and other expert level certifications from Citrix, Extreme Networks, Nortel ERS, and Infoblox. He is currently working to obtain a CCIE in Data Center. He graduated with a MS degree on Systems Engineerin from Birla Institute Technology Science (BITS Pilani)

Suresh  Vs is a Customer Support Engineer in High-Touch Technical Services (HTTS) at Cisco Bangalore, India. He has over 11 years of industry experience working with large Enterprise and Service Provider networks. He has been working with HTTS from past 4 years and supporting LAN Switching and Data center Products. His areas of expertise include Cisco Catalyst 2000, 3000, 4000, 6500 and Cisco Nexus 7000 Switches. Suresh holds a Bachelor's of Sciences in Electrical and Electronics Engineering from Madras University. He has these certifications: CCNA, CCNP, CCIE Data Center (# 46658).

Find other  https://supportforums.cisco.com/expert-corner/events.

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Please be sure to rate the Answers to Questions

[Sarah Staker]

Hello Chandan and Suresh,

I need to know if here is any specific software and/or hardware requirement in order to run FabricPath.

Can you let me know?

Best Regards,

Sarah

[Suresh Vinayagam Subramanian]

Hello Sarah ,

The Nexus 7000 features two kinds of IO Modules: M series and F series.

M I/O Modules cannot switch FabricPath traffic

Only F I/O Modules support Fabricpath .

Hardware Requirement : "F "I/O Modules - F1, F2 and F3 supported 

Software Requirement : Minimum  5.1.1 with F1 and 6.0.1 with F2 I/O module .

Also need to have Enhanced L2 license to run Fabricpath .

you can find more details about different types module and supported features in below link .

http://www.cisco.com/c/en/us/products/switches/nexus-7000-series-switches/models-comparison.html#~f-series

Thanks,

VS.Suresh .

[alejandro.atriano]

Hello Channan and suresh, we are looking to set up a call center which will have 250 phone operators, what kind of switches and routers do you recommend us to use?

Cheers and 

[chsarkar]

Hello Alejandro,

Cisco delivers a comprehensive portfolio of switching solutions for Enterprise Networks, data centers, and smaller businesses. Below CCO link has the details on it.

http://www.cisco.com/c/en/us/products/switches/index.html

For more specific sales requirement, I would request you to check with Cisco Sales or with your partner.

Thanks,
Chandan

[Basavaraj Ningappa]

Hello Chandan/Suresh,

We have a very strange problem in our network with regards DHCP server. We have two nexus 7K running in the core and we have implemented redundancy using HSRP between the nexus 7K. recently we are facing very strange problems with the DHCP server, we have a DHCP server directly connected to nexus 7K and we have so many users vlans where we have enabled “ip dhcp relay” in each svi interfaces and everything was working fine for years.

 Few weeks backs users started complaining that they are not getting the ip address from the DHCP server, we have verified the configuration and we have not done any changes in the network and we tried to run the debugs on the core, we didn’t see any errors or logs.

We tried enabling and disabling the “DHCP service” on the core switch and it helped for some time and after that issue started again. As a work around I have created a layer 3 interface in all of the edge switches and configured DHCP helper addresses and it started working again.

Could you assist me why these nexus 7K suddenly stopped working, have you faced this kind of situation in the fast? 

How do I find that why nexus 7K dhcp relay is not working?

Thanks/Basavaraj

[chsarkar]

Hi Basavraj,

Thanks for writing to us. Here, I would like to ask you few questions to understand if troubleshooting has been touched at all respective areas.

1. Was there any configuration changes done either at the Server end or anywhere in the data path ?
2. At the time of issue, did you perform any packet capture at Server end to check if pkts are received or not ? Or packet capture at Nexus Switches to check if relay pakets are forwarded.

If there are no changes done anywhere, then there are lot of deep troubleshooting which can be performed in order to investigate it further - 

==> Perform packet capture at Nexus to check if packets are indeed hitting to nexus box or not. You can start with ethanalyzer to confirm if DHCP DISCOVER packets are seen on the switch. DISCOVER packets are broadcast and should be seen at the CPU if we have the SVI for vlan unless dropped by CoPP or other reasons.

Below CCO link on how to perform Ethanalyzer :

http://www.cisco.com/c/en/us/support/docs/switches/nexus-7000-series-switches/116136-trouble-ethanalyzer-nexus7000-00.html

==> If you do not see DISCOVER packets, then perform ELAM to track this packet.You should see packet to be destined to CPU. This is to verify if Nexus box is dropping the packet or may be it is putting in to wrong interface.

Below CCO link on how to perform ELAM :

http://www.cisco.com/c/en/us/support/docs/switches/nexus-7000-series-switches/116646-technote-product-00.html

==> Check CoPP drops :

http://www.cisco.com/c/en/us/support/docs/switches/nexus-7000-series-switches/116043-copp-nexus7000-tshoot-00.html

Above are the few things, which would help you to investigate the area we need to focus on.

This forum is particularly on Troubleshooting Fabricpath and its operations.

I would request you to post this question on the below right forum : 

https://supportforums.cisco.com/community/6016/lan-switching-and-routing

Also you can raise a TAC case to check if there are any known related bug to the code you are running on your Nexus 7000 switches

Let me know if you have any questions.

Thanks

Chandan

[chsarkar]

Hello Basavraj,

Let me know if it helped you to troubleshoot.

Regards, Chandan

*** Please be sure to rate the Answers if you find useful ***

[vvvvvbbb123]

Hi Both,

I have heard that Fabric path in cisco has introduced its own data plane. Could you please let us know more on that.

Also Can you think of any use cases for running both LAG and ECMP concurrently between a leaf and spine pair ? I’m wondering if there are operational benefits, allowing you to seamlessly move a physical port between LAGs and FP uplinks to achieve better load balancing?

Regards,

BV

[Suresh Vinayagam Subramanian]

Hello, 

Thats a great question.

Q- Also Can you think of any use cases for running both LAG and ECMP concurrently between a leaf and spine pair ? I’m wondering if there are operational benefits, allowing you to seamlessly move a physical port between LAGs and FP uplinks to achieve better load balancing?

Ans : Let me brief, FabricPath brings Layer 3 routing benefits to flexible Layer 2 bridged Ethernet networks. There is No STP inside. An arbitrary number of routed interfaces can be created at the edge or within the fabric.

I assume what you mean is configuring LAG with ECMP without Fabricpath. In this scenario, redundant links/LAG would be in blocking state due to STP. But by using fabricpath, we can have arbitrary number of forwarding interfaces between spine and leaf.

However, you can run LAG on Edge devices where you have server connectivity ( VPC, VPC+ ),

Q- I have heard that Fabric path in cisco has introduced its own data plane. Could you please let us know more on that.

Ans : Dataplane forwarding in Fabricpath is strictly based in fabricpath Switch ID. I am sharing you below link which has details on Data Plane forwarding.

http://www.cisco.com/c/en/us/products/collateral/switches/nexus-7000-series-switches/white_paper_c11-687554.html#_Toc371593080

Thanks,

VS.Suresh 

[vvvvvbbb123]

Yep Suresh, STP will block LAG..!! Thanks for the explanation...

[Vijay Bhargav]

I understand that Fabricpath uses IS-IS for the control-plane? Do i need to run IS-IS in fabricpath switch ? is there any recommended configuration for ISIS?

Regards,

Vijay

[chsarkar]

Hello Vijay,

Thanks for highlighting this question.

Layer 2 IS-IS protocol works automatically once you enable FabricPath, but you can optionally configure the parameters. There are few FabricPath Layer 2 IS-IS parameters you can configure globally and some you can configure per interface.

Setting Advanced FabricPath Layer 2 IS-IS Parameters

http://www.cisco.com/en/US/docs/switches/datacenter/sw/5_x/nx-os/fabricpath/configuration/guide/fp_advanced.html

Thanks,

Chandan

[Vijay Bhargav]

thanks you :)

[kthned]

Hi

Cisco nexus 9K ... does it support fabricpath...