How to Bypass NAT for LAN to Use Public IP Addresses

ciscointernetipnat;

I have a pool of public IP addresses of 203.82.x.x/28 which is running with PAT/Overload with a private IP subnet of 172.22.x.x on a Cisco 2900 series router.

The radio modem Ethernet link connects to the router interface with a public IP address, and the LAN connects to another interface of the router with a private IP address; a simple configuration.

I know I can split the connection from the radio modem, and put it directly into my LAN switch, using the public network with my LAN hosts. It works fine.

I wonder, how do I bypass the NAT configuration so that I can just change LAN hosts IP addresses to public IP addresses and access the Internet directly, without splitting the connection from the radio modem?

Please correct me If I am thinking wrong.

Best Answer

I am not sure if this is recommended but yes you can achieve it.

The reason you needed NAT there as you cant assign same subnet's IP on R2's access facing LAN interface, if you could , then you could use the same subnet , right?

192.168.1.1/24 .2/24
R1(PE -ISP) ------> R2 (CE) -----> R3 (access- internal)

So, you can achieve it by BVI, config is as below, its simple

bridge irb
bridge 1 protocol vlan-bridge
bridge 1 route ip



interface FastEthernet0/0
 no ip address
 duplex auto
 speed auto
 bridge-group 1
!
interface FastEthernet0/1
 no ip address
 duplex auto
 speed auto
 bridge-group 1


interface BVI1
 ip address 192.168.1.2 255.255.255.0

you can change the IP address and interface as per your scenario.

Let me know if any question/issue or how it goes. Sorry, if i misunderstood your question.

Regards, Lalit

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