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Contributor I

Default size of SAP MTU on 7240 controller?

We have a couple of new 7240s running 6.3.1.2 code that have a SAP MTU setting of 1300.  Did the default size change from 1500?  These were set up by another tech so I am not sure if this was done during config or if the default setting has changed for some reason.

Re: Default size of SAP MTU on 7240 controller?

Is this in the AP sys profile?  Is there a value in that field in the UI?  

Seth R. Fiermonti
Consulting Systems Engineer - ACCX, ACDX, ACMX
Email: seth@hpe.com
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Contributor I

Re: Default size of SAP MTU on 7240 controller?

Yes, this is the AP System default profile.  Currently set to 1300.

Re: Default size of SAP MTU on 7240 controller?

If you see a value in there, it's not the default.
Seth R. Fiermonti
Consulting Systems Engineer - ACCX, ACDX, ACMX
Email: seth@hpe.com
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Contributor I

Re: Default size of SAP MTU on 7240 controller?

So the default is blank which would be auto discovery of MTU size?

Re: Default size of SAP MTU on 7240 controller?

According to this post, default size is 1576 when field is left blank: http://community.arubanetworks.com/t5/ArubaOS-and-Controllers/Oversize-jumbo-frame-errors/m-p/5421/highlight/true#M1860

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Contributor I

Re: Default size of SAP MTU on 7240 controller?

I see that it says it sends 1576 byte frames to detect if jumbo frames are supported, but it doesn't really address how it would determine MTU size if left blank.

Re: Default size of SAP MTU on 7240 controller?

I'm sure there's logic built into AOS that says if the value is blank than use a default value (I assume 1576 based on the link provided).  I can't find anything in the reference guides as conclusive proof, but I think you would find this to be true if you removed the current value and performed a packet capture where the AP is connected.

 

--- Edit ---

 

Just found the following command that should show you the SAP value.  You could try deleting the current value and then issue this command:

 

show ap debug received-config ap-name XXXXXX

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Contributor I

Re: Default size of SAP MTU on 7240 controller?

Good call!  I have tested this and it does indeed default to 1500 when this field is left blank.

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