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sg500x stacking - can you LAG stacking ports?

Answered Question
Jun 15th, 2012
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I have 2 questions about stacking with the sg500x switch.  We have 3 of them.


question #1 - can we LAG two stacking ports together, to increase the stack bandwidth to 20gbps?  I'd like the increased bandwidth, and you can LAG the regular 10G ports together but the manual and the admin UI doesn't appear to support two stacking connections between two switches.


question #2 - the manual indicates that you can configure all 4 10G ports as regular or stacking ports as needed.  However, after digging a bit it appears this may be an error in the documentation.  Elsewhere in the documentation it mentions that by setting the stack configuration to "standalone" the 2 stacking ports will automatically be reclaimed as standard non-stacking ports.  So that explains how to get all 4 configured as regular ports, but how do I configure all 4 ports as stacking ports?  Of course, this doesn't matter with my configuration if I can't LAG two stacking ports together.  My hope was to have 2 10G ports to each switch from each of the other 2 switches.  Like this:


switch A S1 & S2 <->  switch B S1 & S2

switch A S3 & S4 <-> switch C S1 & S2

switch B S3 & S4 <-> switch C S3 & S4

Correct Answer by rocater about 5 years 2 months ago

Hello Robert,


1- Unfortunately you can not LAG the stacking ports. The other port will shut down and act as a backup.


2- I will double check the documentation on this one, however, I can tell you that only one set of 10G ports can be used as stack ports. As you mentioned, in standalone, you can reclaim them for regular use.


Might I offer as a suggestion- If you are really set on getting the 20G link, you could set all the switches to standalone and use several LAGs between them. This would add additional work as each switch must now be configured individually, but it would allow you to complete your design.

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Correct Answer
rocater Mon, 06/18/2012 - 06:29
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Hello Robert,


1- Unfortunately you can not LAG the stacking ports. The other port will shut down and act as a backup.


2- I will double check the documentation on this one, however, I can tell you that only one set of 10G ports can be used as stack ports. As you mentioned, in standalone, you can reclaim them for regular use.


Might I offer as a suggestion- If you are really set on getting the 20G link, you could set all the switches to standalone and use several LAGs between them. This would add additional work as each switch must now be configured individually, but it would allow you to complete your design.

socalrobg Tue, 07/03/2012 - 08:30
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Thanks for the response. I did as you suggested, re-configured all 3 as standalone, then setup ports XG1 & XG2 in a LAG on switches A & B and connected them with 2 SFP-H10GB-CU1M SFP+ Copper Cable modules.  Interestingly, the LAG speed shows as 1000M when I would have expected it to show as 10G.  I haven't run tests yet to determine if this is just a display issue or what.

I intend to then connect switch A & C using a LAG on ports XG3 & XG4 using SFP-10G-SR SFP+ optical module.


FYI - the documentation wording which was a bit confusing was on page 51 of the 500 Series Admin Guide.  Under "stack ports" it had this text,

"You can manually reconfigured S1/S2 and S3/S4 as network ports or stack ports as desired.  All the stack ports on a device operates in standalone mode will automatically become regular Ehternet network ports."


This suggested to me that all 4 ports could potentially be configured as stack ports. The wording could be a bit more precise.

rocater Tue, 07/03/2012 - 09:02
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Gald to hear everything is working for you at the moment. When testing the speed over the link, remember that you will have to generate multiple connections. This is due to the way the LAG balances connections.


Also I have noted the admin guide as you mentioned. It should say that line applies to the Sx500 and not the SG500X. Sorry for any confusion.

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