EXOS: Locally Administered MAC Address

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New EXOS 22.3 brings a new feature "Locally Administered MAC Address".

Based on manual etc. i cannot get in which case this helps me. Unfortunately in manual, release notes etc. there always the one and the same use case described but that does not explain fully transparent to me.

Is somebody out there how use this feature and can tell me what is the problem and how LAA helps ?

Thanks for your feedback.

Regards,
Matthias
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M.Nees, Embassador

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Posted 8 months ago

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Paul Thornton

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Looking at the user guide, it looks like this is a way to have the switch participating in multiple STP domains on different ports where there's a need to have different source MAC addresses (not have every BPDU leaving the switch with the same source MAC - which may confuse other devices in the network).

I can't personally think of an exact use case for this, but it is one of those tools that could be useful in a troublesome L2 STP problem.

This is also a slightly unusual definition of setting a Locally Administered MAC - I would normally interpret that feature as something which let you globally set the MAC address of the switch.  That has two use-cases that I can think of:

1) Your organisation has its own block of MAC addresses from the IEEE and you use these in production (maybe for VMs or something) and you have a policy to use them on networking equipment too.  Slightly unlikely, I agree, but possible...

2) You need to swap out a switch acting as a router connecting to 3rd party systems, and they have a MAC lock on your port.  This is common at Internet Exchanges, and if you have a failure in the middle of the night, it is sometimes easier to just configure the MAC address of the new switch to match the old one to stop port security problems.

Paul.
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M.Nees, Embassador

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Hi Paul,

thanks for your reply but it does not help me ....

The command is "enable switch locally-administered-address".
So you cannot set any own defined MAC address

From my point of view you can seperate the use MAC for STP (06:xx:xx:xx:xx:xx) and the MAC for all the things the switches does (= Management).

But at the end my question is still here - what is a meaningfull use-case for this.

Regards,
Matthias
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Paul Thornton

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I kind of agree with you - I can't see exactly where you'd need to do this, except in a complex network (with maybe multiple vendors) where the fact that the switch management MAC and the BPDU MAC is the same causes a problem.  The user guide suggests this is what it is for.

Personally, and maybe I'm being cynical, but this command has all the hallmarks of a customer coming to Extreme and telling them how many millions of dollars they would be spending on switches if only there was a way to have STP use a different MAC address to the switch MAC.  So the command gets implemented (especially as it is likely an easy thing to do).

I wouldn't worry about knowing the use case for all of the commands - knowing there's a tool in the tool box for doing this may be useful one day, who knows!

Paul.