benefits of adding a nexus switch to datacenter

[prakavi]

                   Hi,

We have  two catalyst 6506 switches  with 10 gb u plinks  and around 120 edge switches cat 3750-x switches. Still the module on the  core wheere servers are connected  is 1000mbps port.Now if we induct a nexus switch to the datacenter what kinds of benefits we can reap In a virtulised environment as well as real  environment?following are the some of the queries.

1- Can we reduce the number of edge switches? ( by virtual environment)

2- Inter operabaility between cat ios and nexus ios,  how this will affect the environement

3- What will be the over  all benefits ?

4- What are the cons of this induction ?

Regards

prakavi

[Reza Sharifi · Accepted solution]

Hi Prakavi,

A FEX need to have a parent switch.  The parent switch is usually a set of Nexus 5Ks or 7Ks.  The FEX doesn't operate on its own and it is dependent on 5ks or 7ks. The image running on a FEXs is usually pushed to it via a 5k or 7k switch.

1- Can we reduce the number of edge switches? ( by virtual environment)  

As also Leo and Jerry already have mentioned here, you only manage the parent switch. So, if you a row of 10 cabinets in your data center and have a FEX in each cabinet with 2 5ks (one in cabinet 1 and one in 10) you only manage the 2 5ks.  It doesn't necessarily reduce the port count, because you have to connect a server to some kind of port, whether that port is connected to a FEX, 5K, 6500, 3750, etc... what it saves you is managing and maintaining fewer devices. Now if you virtualizes your servers and use for example UCS, IBM, HP, etc.. with VMs, that will reduce your port count significantly.

2- Inter operability between cat ios and nexus ios,  how this will affect the environement

Yes, the Native IOS interoperable with Nexus OS very nicely.  Once you start using Nexus OS, you will see that it is much easier to use than IOS.

3- What will be the over  all benefits ?

4- What are the cons of this induction ?

For these last 2 questions you have to evaluate your environment, application and also cost, which is very important these days unless you have unlimited budget. As others also noted, the 6500 series has been around for a very long time and they are very feature rich.  For example, if you are planning to add a Firewall Service Module to your design, than that is only supported on the 6500 and not the Nexus. So, is ACE module, WAN modules, etc...

Overall, Nexus switches are low latency devices with high backplane speed and a lots of througout for data centers, but one could argue that they could also be used as core devices.  At the end it, all depends on your budget and requirement.

HTH

[prakavi]

Dear Reza,

As always you scores! well explained.But I have some more doubts to clear.From your explanations what I understand is  that Nexus is mainly a datacenter switch.Still it can be used as a Core .But  the flexibility of adding linecards is limited.

I have some more queries.

1-Can a FEX  replace a stack of switches?If i have a stack  of 5 switches over 15 floors  can i replace the stack in each floor with a FEX?(irtulized environment)

2- Since we have cat 3750x  swiitces on edge and cat6506 with 10g at the core the aggreagation is not bad.But if i can replace the 3750s with FEX really its helpful.

3-Another question is that   can i have a FEX  each rack where  cat3750s are deployed?

4-All the servers may not support 10G .So will it be an issue?

5- Another option for me is that  replacing the 1gb in the core where servers are connected  with a 10 gb module. it will be less costlier than a NEXUS

my main query was whether we can  reduce the number of edge switches ? I dont think its not possible. Any way I am looking for your valuable suggestions.

Regards

prakavi

[Jerry Ye · Accepted solution]

1. It is possible but you have to understand what is supported with/by the FEX. Like you said, the Nexus is mainly for DC. FEX fabric interface has a 300m limit (from my memory), no 10mb support and no POE (since you said you have 3750X).

2. See 1.

3. See 1. Also, looks like you need L3. With the L3 module inserted into the N5K, this will reduce the number of FEXs to 8.

4. N5K support both 1G and 10G SFPs. And beside, if you use FEX, there are both models, 2248 supports 100/1000 and 2232 supports 1G/10G.

5. You have to decide if you want Nexus 7000 or Nexus 5500. The Nexus 5500 is less expensive when comparing to the Catalyst 6500.

Jerry

Sent from Cisco Technical Support iPhone App

[prakavi]

Hi, thanks jerry for the explanations!

[Reza Sharifi · Accepted solution]

Hi Prakavi,

As always you scores! well explained.But I have some more doubts to  clear.From your explanations what I understand is  that Nexus is mainly a  datacenter switch.Still it can be used as a Core .But  the flexibility  of adding linecards is limited.

Maybe I did not clearly explain this in my previous post. With 5k and 7k switches you actually have more flexibility to add line cards.  For example, with the latest release of Nexus OS (6.1), and Sup-2E,you can now have 48 FEXs per 7k. another word, imagine a chassis with 48 blades in it. Here is link for more info (see table-2).

http://www.cisco.com/en/US/docs/switches/datacenter/sw/verified_scalability/b_Cisco_Nexus_7000_Series_NX-OS_Verified_Scalability_Guide.html#reference_3AD0536C32FF4B499A0936409729951D

1-Can a FEX  replace a stack of switches?If i have a stack  of 5  switches over 15 floors  can i replace the stack in each floor with a  FEX?(irtulized environment)

You can, but remember if for example you are using POE on your 3750 switches, the FEX will not support that. You really have to look at your applications and requirement, functionalist, feature set you need before your replace your 3570s with FEXs.

2- Since we have cat 3750x  swiitces on edge and cat6506 with 10g at the  core the aggreagation is not bad.But if i can replace the 3750s with  FEX really its helpful.

That is not bad design at all.  If your core 6500 switches are not running in VSS mode and you are using spanning on your upliks from the 3750s to the 6500, You can convert them to VSS and use Portchannels to connect the stack of 3750s to the VSS pair.  For VSS, you would need Sup-720-VS or Sup-2T. You would also need to purchase 6900 series or 6800 series card, but VSS would eliminate spanning tree, VRRP, HSRP, and much more overall throughput. You are basically using all your links from the 3750s instead of one forwarding and one booking.

3-Another question is that   can i have a FEX  each rack where  cat3750s are deployed?

Not sure about this question but yes you can connect 3750s to 7ks or 5ks.

4-All the servers may not support 10G .So will it be an issue?

yes, not all servers need to be 10Gig.  For example the 2248 FEX comes with 48 ports of 100/1000 copper.

5- Another option for me is that  replacing the 1gb in the core where  servers are connected  with a 10 gb module. it will be less costlier  than a NEXUS

Defiantly cheaper to buy 10Gig modules for existing 6500 and connect them.

If your servers have dual 10Gig uplinks, you can use VSS for the data center too.

Here is good doc to read on VSS:

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps9336/prod_qas0900aecd806ed74b.html

HTH

[prakavi]

Dear Reza,

Once  agaian I dont have words to express my thanks. The following points are very important to me.

1- FEX   doesent support   POE (so number of edge switches cannot be reduced)  and the distance limit is 300(asper jerry) which is a limitation.

2-Having an infrastructure with cat6500 setup it is better to add 10 gb modules  in the core for the servers and  to implement  VSS  for avoiding spanning tree issues.

3- Ultimately you need endless budgets  ! (very well said)

4- So it is better to stick on to current desgn  and look in to the VSS  concept.

Let me thank all the people who helped and supported. Every one helped with their own contributions. Thnaks a lot again.

Best regards

prakavi

[Jerry Ye]

Correction, the distance between FEX and N5K can be upto 10km away depends on the SFPs (SR SFP is 300m and LR SFP is 10km). Sorry for the confusion.

Regards,

jerry

[Leo Laohoo]

For example, if you are planning to add a Firewall Service Module to your design, than that is only supported on the 6500 and not the Nexus.

A new FW/ASA, NAM and WAAS service module for Nexus 7K should be announced very, very soon.

1-Can a FEX  replace a stack of switches?If i have a stack  of 5 switches over 15 floors  can i replace the stack in each floor with a FEX?(irtulized environment)

As what Jerry has mentioned, the CURRENT Nexus family of switches are aimed at Data Centre switching.  Take note I said "CURRENT".  I am not sure if Jerry is allowed to verify but I heard rumours and the the words "Nexus", "PoE" and "Stacking" were mentioned.

3-Another question is that   can i have a FEX  each rack where  cat3750s are deployed?

Yes you "can" but why bother?   Currently, the Nexus 5K is more feature rich than a 3750X.  The Nexus family was designed to have "looseless" speed so if you want to connect SAN servers to Nexus, you'll see alot of benefits and performance compared to connecting to 3750X switches.  Another benefit of deploying Nexus is Fibre Channel.  3750X will not support Fibre Channel.

4-All the servers may not support 10G .So will it be an issue?

Jerry's covered this up pretty well.

my main query was whether we can  reduce the number of edge switches ? I dont think its not possible.

Depends on the situation, but yes you can.  For example, if you have multiple 24-port 3750X then you just replace this with one 48-port switch.  Understand that this is not your main concern.  Your main concern is the number of logical swithches you need to manage.  With Nexus 2K, you don't manage the physical switches.  You manage the 2K from the Nexus 5K or 7K.

One of my favorite functions I've found in the Nexus family switches is the UID light and the port beacon.  This makes patching and troubleshooting very, very easy.