SD Access AP pool

[KevinR99]

Hi

In DNAC we can only define a single AP pool.  Either the AP is auto assigned to that pool by a macro on the AP or we manually assign a port to the AP pool in the port assignment area.  However, this only allows for one pool.

We have a scenario where we are doing a WLC and AP replacement at the same time as an SDA migration.  Some APs are older and need to stay on older controllers and some are new and will go on a new pair of Cat9800's.  However, we will have both types in the SDA network at the same time as the Access switch to Edge migration will get ahead of the AP replacement work.  So I cannot put the older APs in the AP pool because it points to a controller they are not supported on via option 43.  So I thought maybe I could define an AP pool that points to the new controllers and put new APs on it.  With the old APs I thought I could create an L2VN and stretch it outside my fabric, put old APs on it, maintain the external gateway and get directed to the old WLC via the option 43 in that pool.  So I would effectively assign the ports my old APs are on as "User devices (ip-phone, Computer, laptop)" in the port assignment part of DNAC.  I've done this and the port does get put in the vlan associated with my l2VN.  However, my AP never gets a DHCP address.  When I put a laptop on the same pool it does get an address via the helper address on the external gateway.

Is there something the Edge device does when it identifies an AP such that it won't pass the DHCP request unless the AP is in the AP pool?

Thanks, Kev.

[KevinR99]

As an update to this when I put my laptop on the L2VN and it gets a DHCP address I see its mac on the L2 Border as CP-Learn in the external vlan I hand off to.  However, I never see my AP mac in that vlan table.

[KevinR99 · Accepted solution]

Another update.  Fixed.  I had to define the L2VN as Fabric enabled wireless.  Basic error.

[Preston Chilcote]

I wonder if another solution would be to play with the device classifier that IOS uses to identify an AP is plugged into a port.  You can see in slide 58 here that SDA relies on an IOS template to apply the correct vlan.  In theory, I think you could use that normal template for new APs and create your own for old APs.  https://www.ciscolive.com/c/dam/r/ciscolive/apjc/docs/2020/pdf/BRKEWN-2020.pdf

Also,  in case you aren't aware, it is possible to have multiple option 43's for different models APs.  So, you could have new APs point to 9800 and old APs point to aireos controllers based on the optino 60 that the APs present to the DHCP server: https://community.cisco.com/t5/wireless-mobility-knowledge-base/configuring-dhcp-option-43-and-option-60/ta-p/3143572

Not sure that helps you in your scenario, but still a neat trick I think.

[KevinR99]

Thanks Preston.  The L2VN for my legacy APs is suitable for my needs.  One thing I can’t understand is why my L2VN needs to be fabric wireless enabled.  In fact, I did some packet captures and my AP DHCP request got answered and returned to the edge.  It then didn’t get passed back to the AP unless I had fabric wireless enabled.  I thought the AP would just be treated like any other data device requesting an IP address especially since it wasn’t joining a fabric enabled WLC.  No matter though, I’m just curious.  The solution works.

Kev.