The WLC doesn't support Level 3 chained certificates.
A certificate chain is a sequence of certificates, where each certificate in the chain is signed by the subsequent certificate. The purpose of certificate chain is to establish a chain of trust from a peer certificate to a trusted Certification Authority (CA) certificate. The CA vouches for the identity in the peer certificate by signing it. If the CA is one that you trust, which is indicated by the presence of a copy of the CA certificate in your root certificate directory, this implies you can trust the signed peer certificate as well.
Often, the clients do not accept the certificates because they were not created by a known CA. The client typically states that the validity of the certificate cannot be verified. This is the case when the certificate is signed by an intermediate CA, which is not known to the client browser. In such cases, it is necessary to use a chained SSL certificate or certificate group.
Support for Chained Certificate
In controller versions earlier than 220.127.116.11, web authentication certificates can be only device certificates and should not contain the CA roots chained to the device certificate (no chained certificates).
With controller version 18.104.22.168 and later, the controller allows for the device certificate to be downloaded as a chained certificate for web authentication.
Level 0—Use of only a server certificate on WLC.
Level 1—Use of server certificate on WLC and a CA root certificate.
Level 2—Use of server certificate on WLC, one single CA intermediate certificate, and a CA root certificate.
Level 3—Use of server certificate on WLC, two CA intermediate certificates, and a CA root certificate.
WLC does not support chained certificates more than 10KB size on the WLC. However, this restriction has been removed in WLC 22.214.171.124 and later releases.
Note: Chained certificates are supported for web authentication only; they are not supported for the management certificate.
Currently some of the major CA's (For example Go daddy and VeriSign ) have started providing Level 3 certificates and have stopped providing Level 2 certificate .
We have already opened a bug for the same and will be resolved in next coming releases. (No ETA available).
CSCtk65761: Need to fix Generate CSR for Third Party Chained certificate document .
VeriSign and Go Daddy, two of the most prominent certificate authorities are now using level 3 certs for all customers
using SSL certs. However the WLC does not support Level 3 certs as of now, going forward this would be an issue as
majority of our customers are using VeriSign for the third party certs on the WLCs
Please note that:-
- VeriSign has a work around in place right now where only Managed PKI SSL customers can
generate a CSR using the 'Old premium SSL" as their server instead of an Apache.
- This will generate a cert which would be like the old certificate with only one CA Intermediate
This work around is in place only for an year through VeriSign.
Video - Installing a 3rd Party SSL Certificate for Guest Access