I have 5 public IP addresses from my ISP can I have two firewalls using them?

I have usable 5 public IPs lets say 17.18.1.15-17.18.1.20 from my ISP.

I currently have an ethernet cable connecting my single Cisco firewall to my ISP's router.

Is it possible for me to plug the ISP router into a switch and then have 2 firewalls also plugged into other ports on the switch and configure one firewall to use part of the public IP range and the other firewall to use the other half?

I have heard this is possible but have never tried. Thanks.
MikeC7Asked:
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JohnBusiness Consultant (Owner)Commented:
You need a router for each public IP address (or a router with multiple WAN ports). I have clients with multiple IP addresses and I use a router for each connection I need.
Ken BooneNetwork ConsultantCommented:
Yes what you are asking is possible if the public IP address space is sitting between the ISP router and your firewall.  

The scenario would be like this

        IPS router at x.x.x.1
                        |
        ---------Switch----------
        |                                |
Firewall #1              Firewall #2
x.x.x.2                      x.x.x.4


You can then use say .3 on firewall #1 for something else and .5 on firewall #2 for something else.

This will work without problem.
Thomas GrassiSystems AdministratorCommented:
John is correct

We have a switch after the ISP device.

Then from that switch we can plug in any router device we need to get a separate public address


                                                    ISP
                                                      |
                                                  SWITCH
                                 ______________________________________
                                 |                           |                                  |
                             Firewall 1        Firewall2                        Test
                               
                                                 
This works well  we plug in a Buffalo WiFi Router to the WAN Switch and then we can test WiFi or Lan issues.

HTH

Tom
mjhangiani2Commented:
yes you can use two firewalls each with a unique ip address from the 5 -address block that you have been assigned. Ie router 1 can have address 172.18.1 15 and router2 can have address 172.18.1.16.

However if you plan to use NAT or PAT to hide your LAN using the public address block given to you , then care should be taken that translated addresses used on the two routers are unique too. Ie router1 and router2 should not be configured to NAT the internal address to the same public address.

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MikeC7Author Commented:
Thanks for the feedback everyone! I will give this a try this week!
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