Is there anything wrong with this picture ?

Unanswered Question
Apr 16th, 2012

I was wondering why do i see the Public IP on Fa0/0, and NVI0 at the same time ? The IP is only configured on fa0/0

router #sh ip int bri

Interface                  IP-Address      OK? Method Status                Prot


FastEthernet0/0     YES NVRAM  up                    up

FastEthernet0/1            unassigned      YES NVRAM  up                    up

FastEthernet0/1.1      YES NVRAM  up                    up

FastEthernet0/1.10     YES NVRAM  up                    up

FastEthernet0/1.100    YES NVRAM  up                    up

FastEthernet0/1.101    YES NVRAM  up                    up

Serial0/2/0                unassigned      YES NVRAM  administratively down down

NVI0                YES unset  up                    up

I have this problem too.
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Leo Laohoo Mon, 04/16/2012 - 16:52

Kindly post the output to the command "sh run interface fast0/0"?

love2xlr8 Mon, 04/16/2012 - 16:57

There you go::

interface FastEthernet0/0

description to ISP

ip address

ip nat outside

ip nat enable

ip virtual-reassembly

duplex auto

speed auto


Jan Hrnko Mon, 04/16/2012 - 17:08


I think that everythink is just fine. NVI is just NAT virtual interface which is enabled for NAT purposes. The NVI takes the first IP address of the interface where the command ip nat enable is configured.

Best regards,


love2xlr8 Mon, 04/16/2012 - 17:15

everything wokrs fine for the most part, but I can't ping that IP from anywhere inside outside .. even from within the router itself..

Jan Hrnko Mon, 04/16/2012 - 17:33


what kind of NAT are you configuring? NAT with ip nat inside and ip nat outside commands or the NVI?

As far as I know there should be either the commands :

ip nat inside and ip nat outside commands


ip nat enable command

But I see that you have also the ip nat enable configured on fa0/0 interface. Isn't that making any trouble?

If you are configuring the NVI please reffer to this guide:

Best regards,


love2xlr8 Mon, 04/16/2012 - 17:45

Hey Jan,

I'm not configuring the NVI nat, but IP NAT inside and outside..

Thank you

Jan Hrnko Mon, 04/16/2012 - 17:52


So what about the command ip nat enable? Can you try to clear it by no ip nat enable? If you don't have some production going on I'm not absolutely sure what it will cause...but I think it shouldn't be there unless you are configuring the NVI.

Best regards,


love2xlr8 Mon, 04/16/2012 - 18:00


I removed that statement, but it don't seem to make a difference.. I still can't ping that interface for the router itself .

Jan Hrnko Mon, 04/16/2012 - 18:29


this is an strange problem indeed. I am trying to simulate it in GNS3, what kind of device do you use? Maybe it is because of the NVI getting the same IP, but I am not able to replicate this scenario right now. I will inform you as soon as I find something out...maybe someone will get to the root of the problem by that time, but anyway, I will try to solve the issue in the meantime. Everything else is ok so far? Only the ping from the router on the interface won't work, is that right?

Best regards,


love2xlr8 Mon, 04/16/2012 - 18:38


Thanks _ I greatly appreciate your assistance... As i said everything is working for the most part, NAT traffic is going in and out however I do have some issue with my CME which i think is related to this issue..

love2xlr8 Mon, 04/16/2012 - 18:46


Plase see attached the config file, I have modified the Public IP's since this is a public forum,everything else is untouched..


Edit: Someone with name J. posted asking for the config, but he deleted his post for some reason.. I'll leave the configs in case he decides to take a look

Message was edited by: love2xlr8

John Blakley Mon, 04/16/2012 - 18:52

I deleted my post after seeing that you had it fixed already Are you having any other issues still?

love2xlr8 Mon, 04/16/2012 - 19:05


I'm troubleshooting some CME issues, but i believe its all tied together..

Nat and everything works well, but I can't ping anything outside from this router, even its own WAN interface.. Shouldn't I be able to ?

John Blakley Mon, 04/16/2012 - 19:11

Is this in production? If not, try to remove your outside static nats to see if you can ping. You can also try to ping out sourcing from one of your inside addresses. You should be able to ping your gateway from the router. Are there any other devices involved?

love2xlr8 Mon, 04/16/2012 - 19:21


I am able to ping my WAN default gateway, also I can ping from the LAN interface to the wan, not when I ping directly from the router.. odd isn't it?


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