How do I authenticate multiple LDAP via Apache?

If you need to add multiple OU= values in the LDAP url you must have separate LDAP urls and utilize AuthnProviderAlias to check both LDAP searches.

Use the following AuthnProviderAlias to check LDAP searches.
LoadModule authn_alias_module 
<AuthnProviderAlias ldap ldap-alias1>
AuthLDAPBindDN cn=youruser,o=ctx
AuthLDAPBindPassword yourpassword
AuthLDAPURL ldap://
<AuthnProviderAlias ldap ldap-other-alias>
AuthLDAPBindDN cn=yourotheruser,o=dev
AuthLDAPBindPassword yourotherpassword
AuthLDAPURL ldap://
Alias /secure /webpages/secure
<Directory /webpages/secure>
Order deny,allow
Allow from all
AuthBasicProvider ldap-other-alias ldap-alias1
AuthType Basic
AuthName LDAP_Protected_Place
AuthzLDAPAuthoritative off
Require valid-user