What version of code are you running on the 3000? Only 3.6 supported CRL checking via HTTP.
If you go to the Admin - Certificate Mgmt - Configure CA Certificate screen, there's box options for which protocol to use, you can select HTTP in there. You cna then also enter in the URL and you should be good to go.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...