Wow, you dropped all that money on a 4260 and didn't buy the 4 Cu interface card bundle?
You're only option (besides buying a much more expensice 4 port card) is to use VLAN pairs to go in and out of your 4260. One limitation of doing this is the Single GigE interface will have to carry both directions of traffic (to and from the sensor) on the same interface. This will reduce your effective throughput to half of the interface's capicity.
Create a new VLAN in your switch. Take the existing VLAN that was going to the WAN router (I HOPE your IPS is INSIDE your Firewall) and put them both in a trunk and send them to your 4260. Set up a VLAN pair for those two VLANS on the 4260. Put a new interface on your switch in the new VLAN you just created and cable that to your WAN router.
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...