Is this a bug : I do not need to apply NAT in order to go to ISP?

i couldn't solve this problem. The bizarre thing is that i can go to ISP without applying NAT on lab_B inside packet tracer. What i did was just running routing process at most. So, why should we map private into public IP addresses in this scenario? (in case where lab_B tracks through ISP and the remote host)

http://rapidshare.com/files/455423588/Access_control_list_ornegim_NAT_yapamama_sorunu.pkt

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Comments

alan2308

The reason that you should do NAT is because private addresses are not routable on the Internet. It just wouldn't work if there were 5000 hosts using the address 192.168.1.100.

The ISP should be dropping all packets using a private address.

thedrama

alan2308 wrote: »

The reason that you should do NAT is because private addresses are not routable on the Internet. It just wouldn't work if there were 5000 hosts using the address 192.168.1.100.

The ISP should be dropping all packets using a private address.

In this scenario of packet tracer i can send ping packets from human resources users to ISP interface succesfully just by routing (without using NAT/PAT) on lab_B. This shouldn't have been i think.

So where is the problem, i can not find?

alan2308

thedrama wrote: »

In this scenario of packet tracer i can send ping packets from human resources users to ISP interface succesfully just by routing (without using NAT/PAT) on lab_B. This shouldn't have been i think.

So where is the problem, i can not find?

The problem is that in this scenario, you are controlling everything, including the "ISP." The ISP has to manually drop traffic with private addresses, there's nothing in the routers that will do it automatically.

Look at it this way. In your network, where you expect private addresses to be routed, you're using the same router(s) that you're using to represent the ISP. The router's behavior doesn't magically change because you placed it somewhere else.

billyr

I've already answered this for you on another forum.
You are using packet tracer it only acts as you tell it.

okplaya

Try this:

Router 1

interface FastEthernet0/0
description To ISP
ip address 68.68.68.67 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 10.10.10.1 255.255.255.0
duplex auto
speed auto

Router 2

interface FastEthernet0/0
description To Customer
ip address 68.68.68.69 255.255.255.0
duplex auto
speed auto

Laptop

IP - 10.10.10.10
NM - 255.255.255.0
DG - 10.10.10.1

The laptop connect to Router 1. Router 1 to Router 2 (ISP). Sorry can't see your file from my phone.

thedrama

You're right. Even ISP is under my control in the scenario. Nevertheless, you know that my purpose by implementing NAT or PAT is providing them go through outside network cos private addresses are not routable, moreover, public IP address conservation. It also allows private network with many users to use(to be mapped into) only one public address.

I made a research about in which router NAT is implemented however, i can not make a decision about it most of the time.

For example, regarding another sample below, please let me ask a question.
http://rapidshare.com/files/455601543/Netw._address_translation_successfully_done_.pkt

As you can see there are private networks which IP addresses are assigned 172.16.30.0/24 and 172.16.20.0/24. There is a gateway router which I performed PAT on and an ISP which opens to a server.
Once i configured PAT, i wanted to check NAT translation table on gateway router. As i have seen, outside network was shown only as 198.18.0.0/24. it also should have included 11.0.10.0/16 but it was not. Why not ?

Another question, if there were three routers connected to each other, which router i should have applied the PAT ? (the one directly connected to private networks?)