This is a very popular question that is asked at literally every WING5 training (and, I must admit, due to misinterpretation I was giving out the wrong answer, so read this). Getting those link levels is easy, troubleshooting the resulting system instability issues is not easy.
We typically know that single-site scenarios use Level 1 links (up to a certain size) and between sites one always uses Level 2. So what happens when you have local and remote sites, as on the diagram below?
According to the Best Practices and Recommendations document, you must not mix MiNT link levels on the controllers, and must keep controllers in a separate RF Domain:
MINT links levels should be maintained across the whole deployment, mixing MiNT level 1 and MiNT level 2 links on the same controller is not recommended and not supported.
In distributed deployments with multiple remote sites NOC controllers separate isolated RF Domain with no Control VLAN defined.
Thus, we need to transform our diagram into this:
Pretty much, we’ve moved our controllers into a separate RF Domain and local APs are now treated as “local remote site”, with APs adopted over MiNT Level 2 as usual for remote sites. Based on the size of the local site, we have two options on how to implement it:
- <= 128 APs: Just a standard remote site with AP as RF Domain Manager. Make sure to define Control VLAN!
- >128 APs: either split into multiple sites under 128 APs each and see above, or make this RF Domain controller-managed (aka Virtual RFDM). In this case make sure not to define Control VLAN! J
Thus, the golden rule is: it’s either ALL Level 1 or ALL Level 2 on controllers. Mixing MiNT link levels on controllers is not supported: behaviour is not defined and you may see all sorts of weird things. It might actually work, or you might see random AP reboots, controller freezes, SMART RF issues and who knows what. Keeping MiNT link levels within supported guidelines ensures a healthy and stable network. Make sure to consult the Best Practices document and attend our WLN2018 training where you can discuss all this live.
Hope this clarifies all the confusion around this topic. Happy networking!
Arsen Bandurian: Technical Blog 
Hi Arsen! Thank for your interesting and valuable articles! Back to your latest one on MINT levels: Should be a Control VLAN defined also for RF-domain=DC or not, supposing that RF-domain HQ contains <= 128 APs?
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Control VLAN is only needed when AP is RFDM. If Controller is RFDM (single site or controller-managed RF Domain) or there are no APs in RF Domain (DC) – do not use Control VLAN.
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Hi Arsen & Ahoj Radime, Control VLAN should be used when Level 2 is used (exception exist;). That’s the VLAN where RFDM election takes place and winner is the one who keeps the Level 2 link to RFS/NX. MiNT comunication between RFS and remote APs is then proxied through this RFDM.
It’s written between lines, but not mentioned explicitely – when Level 2 is used, cluster link between RFS also has to be at Level 2.
Last point to mention – 128x AP is not always valid limit. There are APs, which can’t exeed 24x AP per RF domain. Also there used to be a rule for mixture of these two kind of APs in one RF domain.
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Actually, the L2 clustering link is explicitly written in the new Best Practices AFAIK, and the new WiNG5 training.
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