How to assign multiple IP in one or sub interface

[fosiulalam]

Hi

I have Cisco 2600 Router .

show ip interface brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            xx.xx.xx.250  YES DHCP   up                    up 
FastEthernet0/1            172.16.0.2      YES NVRAM  up                    up

FastEthernet0/0 is connected to ISP modem, and I used to one static IP Which i used get via DHCP

From running-confnig:

interface FastEthernet0/0
description link-to-bt-router
ip address dhcp
ip nat outside
duplex auto
speed auto
!

Now ISP assign 5 Statci IP which i will get the same way via dhcp .

but whats the best way to get those Ip ?

shall i create 4 sub interface ??and assign, Ip address dhcp under each subinterface ??

I will have to do port forward aswell ..

Pleaes give me some idea with commands

Thanks

[fosiulalam]

HI Rick

Thanks  again

I will give it a try tomorrow Morning when i will go to office . As I am at home.

I will come back to you tomorrow 9 am uK time.

Thanks

[fosiulalam]

Hi Rick

Good Morning

I am trying to following your instruction

(a) I have deleted all  address from fast

interface FastEthernet0/0
description link-to-bt-router
ip address dhcp
ip nat outside
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 172.16.0.2 255.255.255.252
ip nat inside
duplex auto
speed aut

Now Router is getting one of the New Address via DHCP which  is :

1.1.1.226

IP ranges : 225 -229

so i have typed

ip nat inside source static 1.1.1.225 172.16.0.2

ip nat inside source static 1.1.1.227 172.16.0.2

% 172.16.0.2 already mapped (1.1.1..225 -> 172.16.0.2)

what to do now ??

thanks

[fosiulalam]

HI Rick

Just realized something from one of your comments

in my example 172.16.0.15 is the inside address of one of your servers  and 1.1.1.5 is one of the new addresses given by the ISP)

So what you are trying to do is :

Public Ip : 1.1.1.1 will be mapped to internal server 10.0.0.5

public ip :  1.1.1.2 Will be mapped to internal Server 10.0.0.6

right ??

but problem is : all those internal server is behind a Firewall

so all the request will have to forward to firewall address which is : 172.16.0.1

[Richard Burts]

Fosiul

I am glad that you figured out from your previous post that you do not map all the new public addresses to the same inside address. You need a mapping (a static nat configuration) for each new public address to a unique inside address (of the various servers).

The fact that the servers are behind a firewall should not be a problem. The static nat is the same - you need to map each of the new public IP addresses to a unique inside address (it seems that your inside addresses may be 10.0.0.x). So

Public Ip : 1.1.1.1 will be mapped to internal server 10.0.0.5

public ip :  1.1.1.2 Will be mapped to internal Server 10.0.0.6

seems right.

You just need to be sure that there is routing logic on the router that knows that to get to the 10.0.0.0 network it needs to use the firewall 172.16.0.1 as the next hop address.(or maybe you want routes just for the addresses of the servers. which would be best can only be figured out by someone who knows the network topology and its requirements)

And there may need to be some changes made on your firewall.

- it needs to permit traffic from the Internet to the server inside addresses. (which it may or may not do already)

- it needs to not try to translate traffic from the servers on the way out to the Internet. (I would assume that currently it does translate traffic for all inside hosts going out to the Internet)

HTH

Rick