AOS-Switch (2930) failing to download ClearPass CA certificate

tl;dr – Check the clocks, check you the well-known URL on ClearPass is reachable, check you’ve allowed HTTP access to ClearPass from the switch management subnet.

Another in my series of simple issues that have caught me out, yet don’t seem to have any google hits.

When you implement downloadable user roles from ClearPass with an Aruba switch the switch uses HTTPS to fetch the role passed in the RADIUS attribute.

There are a few things you need in place to make this all work but the overall config isn’t in scope for this post. The key thing I want to focus on, that caught me out recently, is how the switch validates the ClearPass HTTPS certificate.

With AOS-CX switches (e.g. 6300) the certificate can simply be pasted into the config using the following commands:
crypto pki ta-profile <name>
ta-certificate
<paste your cert here>

You don’t need the full trust chain either, if your HTTPS cert was issued by an intermediate CA you only need to provide that cert, though it doesn’t hurt to add the root CA as well.

With AOS-Switch OS based hardware (e.g. 2930f) you can’t paste the cert in, your CLI option is uploading it via TFTP.

Fortunately there’s a much easier way of doing this – an AOS-Switch will automatically download the CA cert from ClearPass using a well-known URL – specifically this one:
http://<clearpass-fqdn>/.well-known/aruba/clearpass/https-root.pem

You have to tell the switch your RADIUS server is ClearPass by adding “clearpass” to the host entry – but I did say I wasn’t going to get into the config.

Recently I had a site where this didn’t work. The switch helpfully logged:

CADownload: ST1-CMDR: Failed to download the certificate from <my clearpass FQDN> server

This leads to:

dca: ST1-CMDR: macAuth client <MAC> on port 1/8 assigned to initial role as downloading failed for user role

and:

ST1-CMDR: Failed to apply user role <rolename> to macAuth client <MAC> on port 1/8: user role is invalid

So what was wrong? In this case it was super simple. The route to ClearPass was via a firewall that wasn’t allowing HTTP access.

Other things to check are clocks – both the switch and ClearPass – always use NTP if you can. Also there have been ClearPass bugs introduced in some versions that break the well-known URL so its worth checking the URL is working. There can also be some confusion between RSA an ECC certificates, which ClearPass now supports. The switch will use RSA.

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