Need some help using multiple subnets on WAN interface for 5510

[dbrown]

Hello Cisco Experts!  I've recently taken over a new role from a co-worker and could really use some expert advice.  I'm attempting to setup Outlook Web Access and a secondary MX record over at my failover datacenter.  There I have a 5510 which already has an IP assigned by our ISP bound to the WAN interface.  I purchased a new block of addresses on a different subnet that I'd like to use for OWA and a secondary MX record at my datacenter.  I can't seem to bind more than one public address in a different subnet to the WAN interface which is how I thought this would work.  I further read that the work-around is to use Proxy ARP and NAT.  Being new to this I could really use some step-by-step help in configuring the ASA so the new addresses I have are properly forwarded to Exchange (OWA) and Websense (secondary MX).  I can have Cisco support do it but I want to understand how this works so I can be more useful in the future.  Many thanks in advance for any assistance!

Dan

[Jon Marshall · Accepted solution]

Dan

You do not need to assign the public IP to an interface to use it for NAT. You simply configure NAT and allow the traffic in your acl (if you have one).

What version of code are you running on your ASA because NAT is very different from 8.3 onwards.

"sh run" will show the version right at the top.

Jon

[dbrown]

Thank Jon, after researching this I found you were right.  We are using Proxy Arp just as you describe.