Cisco 4500 Chassis vs 6500 (VSS)

[kmcdonald1973]

Hello, We are preparing to install a new switching Infrastructure at one of our sites. We have decided that we want to have two seperate chassis as a core. My original idea was to purchase 2 - 4500 chassis and install 10Gb and 1GB line cards in each and use STP and HSRP to load balance between the two cores.

We had also contactd a vendor for thier recommendations and they came back with 2 6500 Chassis running VSS. I reviewed what VSS was as I had never heard of it and it looks to me basically to be real close to the same thing as Stacking. I didnt really want to have stacked Cores because I would like to have the flexability to be able to take one core out and update the software or image, reboot, and such without effecting anything on the network. I can do that with the non-VSS approach but it looks like that would be more of a problem with VSS.

My question is, does anyone out there have experience using VSS with the 6500's? Are yoiu able to take one of the VSS pairs off line and not effect normal network operations?

[burleyman]

Actually with VSS you do not even need to reboot the switches at all when you update the IOS so no down time. Ours have been up for 4 years+ and have updated the IOS twice. I also think the 4500's will be coming out with VSS as well. When using VSS the two switches think they are one.

Mike

[Reza Sharifi]

Hi,

In VSS environment, you would need to use eFSU to upgrade one chassis at the time.  Basically you upgrade the stand-by chassis first, reboot it and then upgrade the other switch and reboot.

Here is a link for step-by-step upgrade using eFSU.

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/issu_efsu.html#wp1042706

HTH

[kmcdonald1973]

According to the guide even using eFSU will cause some downtime. The modules restart because of the supervisor switchover so your nor getting any benefit in that regard frem VSS. It acually looks a bit riskier to do the eFSU upgrade because your hoping if the upgrade fails that it will roll back to previous image and just run properly.

I understand VSS is basically just stacking for Chassis and is very beneficial for multi-homing other devices to it but you can still use HSRP and STP to load balence and achive redundancy and stil have the flexability to do maintenace on one Core and not having to worry about a failure giving you an outage.

Am I missing some other great features of VSS I must have?

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Pehaps the two principle advantages of a VSS implementation, faster fail-over than STP/HSRP and/or (easier/possible) multi-link utilization.  The fail-over timing can become critical for apps like VoIP or live Video.

PS:

Yes, modules restart, but if everything is dual homed, traffic should flow through the active VSS device while the other is reloading.

[kmcdonald1973]

Yes it does appear that failover is much faster, according to the link below its a differents of 7 seconds compared to around 330 milliseconds. So depending on your SLA (or what your company can afford to pay) would determine whats acceptable.

It was tested at 648Gbps fabric and thats a alot of traffic but how many companies actually come anywhere near that?

And another "upside" would be the dual homing across the stacks and not wasting a link to STP but depending on your size and capacity requirements, that may be a very small detail as usually 1 primary 10Gb port per VMHost is fine for our needs.

I guess my biggest problem is the fact that both of these VSS pairs are logically the same switch which means when you need to do maintenance there is really no way that you can seperate the two and be able to do whatever maintenance on it for how long you need without ever having to worry about having an impact on your production environment. This can be done fairly easy with HSRP/STP.

I may be a bit too paranoid about the chance of an image upgrade going wrong and having that delay fixing it bleed into production time but Im not so sure.

Any other opinions out there?

http://www.networkworld.com/reviews/2008/010308-cisco-virtual-switching-test.html?page=1

Thanks,

Kevin

[Leo Laohoo]

For the 4500R+E to run VSS, you'll need to be using Sup7E line card.  VSS-support for the Sup7E is slated to be released sometime end of this year (2012) or Q1 of 2013.

Regarding the 6500E VSS solution, what line card was the vendor quoting you on?  You should be looking at the VS-Sup2T and should no longer be considering the VS-Sup720.

In regards to the 10 Gbps line card for the 6500, what line card has the vendor quoted you on?  Not all 10 Gbps line cards will support VSS (particularly if you are quoted the VS-Sup720).

Heck, get Reza to answer all of your VSS enquiries because I think he's "THE" only VSS person in town (outside Cisco, of course!). 

[Joseph W. Doherty]

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

Well there's another point in favor of VSS, as you've noted it make the two physical devices appear as one on the network, but remember besides ease of management (i.e. less devices to manage), less logical devices postpone or improve both L2 and L3 scalability issues.  I.e. there's not only the question of how fast the single device deals with fail-over, but the rest of the network too.

In any case, you can certainly chose to go with the older approach, i.e. two distinct devices.  It really depends what's more important to your service requirements.