There is a lot of pages out there which help with this, but the best I found was http://www.seedsofgenius.net/solaris/solaris-authentication-login-with-active-directory (This link does not seem to work now, so here is a cached version: https://web.archive.org/web/20151101112540/www.seedsofgenius.net/solaris/solaris-authentication-login-with-active-directory) so please go ahead and follow this for more details. I have a cut down version here for Solaris 11.
I will presume you have setup your Windows server (see link above Install UNIX Schema into Active Directory and Create ProxyDN User Account).
Updated: Testing Section (30th October 2012)
Updated: Setup DNS Section (7th July 2014)
Updated: Kerberos testing "kinit -V" (29th January 2016)
Updated: Setup LDAP client "followReferrals=false" (29th January 2016)
Updated: Setup PAM (29th January 2016)
Updated: Tested on Solaris 11.3 (29th January 2016)
Settings being used:
Windows 2008 R2 AD servers = dcsad01 (220.127.116.11) and dcsad02 (18.104.22.168)
Domain = dcs.bbk.ac.uk
Kerberos Realm = DCS.BBK.AC.UK