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2x 3750X : StackWise?

fearless.rabbit
Level 1
Level 1

Hi all,

We are replacing our "core" switch (I dont even wanna tell you what it was) with 2 3750Xs. There is handfull of access 2960s which will be connected using two uplinks: one to first 3750, other to second. Pretty basic design.

Now, Im a small-business networking guy with decent Cisco background, which mostly consisted of GNS3 labing. With that said, my brain immediately went HSRP for redundancy, single IP address for two switches, designated HSRP ports and Im done. Then I saw switches are arriving with StackWise cable, technology I never used before. I know how it works from birds-eye view, but never actually implemented it.

Id highly appreciate some input regarding:

  • With StackWise possible, does considering HSRP makes sense?
  • Do I still need to consider STP? When access 2960 connects to both 3750s, will StackWise take care of loops?
  • What should I configure on access switches? Just put those two uplinks in ether-channel group?

These question might sound stupid, but forgive me because Id like to prepare everything, including myself, for quickest implementation and smallest downtime. Your input will allow me to prepare configuration on paper, and configure new switches up and running in no time. Thank you in advance!

Milos


1 Accepted Solution

Accepted Solutions

Kyle McKay
Level 1
Level 1

Hi Milos,

1) If you are utilizing Stackwise technology there is no point in using HSRP. The stacked switches effectively share the Gateway IP address and if one of them were to fail the other is still there.

2) STP is much simplified when using stackwise technology. You would want to port-channel your 2960 to BOTH 3750 switches - this will look like one logical STP link thus eliminating any STP loops.

3) Yes, as mentioned above - you will ideally create an etherchannel (port-channel) from the access switches to BOTH 3750 switches. (Cross-stack port-channel)

Hopefully this helps !

View solution in original post

11 Replies 11

Kyle McKay
Level 1
Level 1

Hi Milos,

1) If you are utilizing Stackwise technology there is no point in using HSRP. The stacked switches effectively share the Gateway IP address and if one of them were to fail the other is still there.

2) STP is much simplified when using stackwise technology. You would want to port-channel your 2960 to BOTH 3750 switches - this will look like one logical STP link thus eliminating any STP loops.

3) Yes, as mentioned above - you will ideally create an etherchannel (port-channel) from the access switches to BOTH 3750 switches. (Cross-stack port-channel)

Hopefully this helps !

Of course it does, it`s extremely helpfull! It cleared the design questions for me

Joseph W. Doherty
Hall of Fame
Hall of Fame

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

#1 HSRP may make sense.  By default, if the Stack master fails, another member switch becomes the gateway IP but the virtual gateway MAC changes.  As a gratuitous ARP is sent, most modern hosts will reset their ARP cache, but it can be problem for hosts that don't react to the gratuitous ARP.  Two ways to avoid, use HSRP which also has a virtual MAC or use the command that transfers the original stack master's MAC to the new stack master (NB: other considerations with this command also apply).

Another reason for using HSRP, if in the future you wanted to migrate to a new L3 gateway device, you can have it join the HSRP group and take over as the active gateway.  (Probably unlikely needed in your case.)

#2 Depends on what you consider STP need.  STP doesn't pertain to the stack ring, but you'll likely still want it active to preclude accidental edge loops.

For the 2960s, multiple links would require it unless you use Etherchannel or FlexLinks.

NB: BTW, think original STP is default, if so, enable rapid-STP.

#3 Etherchannel, to the different stack members, would be my 1st choice.

Etherchannel on uplinks and stacked 3750s then it is. There will be no need for STP since I wont be connecting access switches to another access switches. Much appreciated!

P.S. This StackWise thing looks very similar to VSS by the way..

P.S. This StackWise thing looks very similar to VSS by the way..

StackWise predates VSS, I believe.

One more lame question.. Do I configure StackWise first, and then continue as configuring one single switch, or do I configure them one by one?

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

StackWise is, more-or-less, automatic.  There are some "knobs" you can touch, but if you interconnect two (or more) 3750s and power them on, you should "see" one device.

PS:

It's best to insure that all stack members have the same IOS version and feature set (license) before stacking them.

Perfect. Thanks a bunch!

fearless.rabbit
Level 1
Level 1

Hi again all,

Neat 3750s arrived, and Im enjoying configuring them Few more things, and they`re ready for production.

I got a quick question regarding EtherChannel. Each of our 2960s will use two uplinks, one to first stack member, one to second stack member. Is anything else required except configuring EtherChannel on both sides - on 2960 and 3750s? Do I just create an EtherChannel and for example add 3750 ports G1/0/1 and G2/0/1 to it?

Thanks,

Milos

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

Basically that's it.  Of course, there's all the options you can configure.  You might want to confirm the particular load balancing algorithm is good for your traffic.

Indeed, just tested it and works like a charm. It`s not instantaneous, but it`s quick. Next step - link aggregation with blade servers

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