How to setup Cisco IOS with multi public IP's

Question

I'd like to set up a little network environment. We have bought 2 different subnet from our ISP. 
The WAN internet connection: xx.yy.81.61/26
WAN gateway: xx.yy.81.1
First subnet : xx.yy.81.80/30    (this has the same first 3 octet as the WAN, probably doesn't count, because it is a different subnet)
Second subnet : zz.uu.156.48/29
As you can see in the first diagram, the xx.yy.81.61/26 is assigned to the CISCO's outside(WAN) interface, the internet connection is alive, all hosts in LAN have internet connection. We want to assign some hosts with public IP address (for webserver sake). I'm not familiar with networking, so please forgive me if I make some silly questions. In brackets, I make the cisco router setup with the "Cisco Configuration Professional 2.8" PC program.
             |     
             |     ADSL or Optical cable (fiber link)
             |
        +-----+
        |        |   modem
        |        |
        +-----+
             |
             |        WAN (xx.yy.81.61/26)
             |     Gateway(xx.yy.81.1)
             |
      +----------+
      |              |
      |              |    CISCO 881 (router/firewall)
      |              |    IOS 15.2(4)M6
      |              |
      +----------+
             |
             |
       -----+-------------   our local LAN segment (vlan)
        10.10.10.1/24
I want to set up the CISCO:
- The question is, that how can i make my subnets alive? I just want to transmit(NAT) some public IP from subnet to specific HOST computer(or inverse?). I have made the NAT rules (zz.uu.156.50 <- 10.10.10.xxx), but no result, the public IP is unreachable(no ping, no traceroute). 
- Do I have to assign a second IP(virtual) address from subnets to the outside interface(WAN). If yes, than how? Or my ISP has to route the subnets to my WAN IP address(xx.yy.81.61) ?
The truth is that the original setup was different, as you can see in the second diagram. In this case the both subnet was alive. Now, I unmounted the ISP owned HP router and I attached the CISCO directly to the modem output(first diagram), because we had some DNS issues and I think it is unnecessary to be 2 router sequentially. Please indicate if i was wrong. 
I mention, that by the original setup, I could access the HP router (only the login interface) from internet with the first IP of the subnets (xx.yy.81.81 from the first subnet and  zz.uu.156.49 from the second subnet).
             |     
             |     ADSL or Optical cable (fiber link)
             |
        +-----+
        |        |   modem
        |        |
        +-----+
             |
             |
             |
       +-------+
       |          |    blackbox, no acces
       |          |    ISP owned HP router
       |          |
       +-------+
             |
             |        WAN (xx.yy.81.82/30)    or      WAN (zz.uu.156.50/29)
             |     Gateway(xx.yy.81.81)            Gateway(zz.uu.156.49) 
             |
      +----------+
      |              |
      |              |    CISCO 881 (router/firewall)
      |              |    IOS 15.2(4)M6
      |              |
      +----------+
              |
              |
        -----+-------------   our local LAN segment
          10.10.10.1/24
Thanks for any answer or suggestion! 

Answer 1

Hey,
Proxy-ARP should take care of this!
As long as you assign the NAT rules into the IOS Router it should start replying to any ARP request to those IPs on different subnets.
Of course the ISP should forward this ARP requests to you!
So make sure Proxy-ARP is enabled in the WAN interface and you should be good to go (as long as the NAT rules are good).
Regards,
Julio Carvajal
Senior Network Security and Core Specialist
CCIE #42930, 2-CCNP, JNCIS-SEC
For inmediate assistance hire us at http://i-networks.us