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Community Member

Cisco 1941 Router- IP nat

I'm noticing in several other engineers' network configurations, that the ' ip nat ' for g0/0 is always set to ' outside '. The ' ip nat ' for my g0/0 int, is currently set to ' inside ' because its a LAN connection, and the ' ip nat ' for my g0/1 int is set to ' outside ', because its a wireless connection.

Do I have my ' ip nat ' configurations backwards, or set incorrectly in my router?? If so, could someone please explain why?

Thanks

- Joey

2 ACCEPTED SOLUTIONS

Accepted Solutions
Community Member

Re: Cisco 1941 Router- IP nat

Joey,

NAT looks like it is configured correctly.  Are you having any issues?

Edit:  Why are you using the route-map to configure NAT?  I may be wrong, but I think you should configure a separate access list.

Bryan

P.S.

For future reference, you should X out ur password "7" keystrings, as they take only a simple google search (or in my case, a simple Ipad App) decode.

Community Member

Re: Cisco 1941 Router- IP nat

Joey,

No problem.  I hope this helped you outl  Just for saftey sake(and frankly, my lack of understanding) I would just create a separate access-list and attach that to the "ip nat source ###" command.  As for the password "7".  When you posted your config, all of the password commands listed under the line commands for "con" and "vty" are easily decrypted.  Just a future reference for you if you need to post a config online like you did here.  As an example:

line con 0

exec-timeout 0 0

password 7

logging synchronous

login local

line aux 0

Replace:

password 7

with:

password 7 xxxxxxxxxxxxxxxxxxxx

Just a heads up for the future.  And I would change your password that you have already configured.

Also, if its not too much of a bother, please mark this question as answered.  Thank you.

Bryan

11 REPLIES
Community Member

Cisco 1941 Router- IP nat

Joey,

NAT is for translating private addresses into the public addresses.  The "inside" will be for the interfaces connected to the local interfaces with the private addresses.  The "outside" will be for the interface connected to a public address.  Check out the link below for more information on NAT.

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080094831.shtml

Community Member

Cisco 1941 Router- IP nat

Bryan -

Thanks for the response. The link was helpful.

So, in my case, I was correct with my configuration(s), seeing as g0/0 is my LAN ( the local 'inside' network ), so ip nat being set to inside was correct, and g0/1 being my wireless ( to the ' outside ' world ), the ip nat being set to outside is correct.

Thanks.

- Joey

Re: Cisco 1941 Router- IP nat

Hi Joey,

I've had this config on your other post. This an example of a dynamic NAT or PAT, that is you translate multiple private IPs to a single public ip.

int g0/1

ip address 192.168.1.254 255.255.255.0

ip nat in

int g0/0

ip nat out

access-list 1 permit 192.168.1.0 0.0.0.255

ip nat inside source list 1 interface g0/0 overload

Sent from Cisco Technical Support iPhone App

Community Member

Re: Cisco 1941 Router- IP nat

John -

So then, I did have my config wrong? Should the ip nat for g0/0 (LAN) be set to outside, and the ip nat for g0/1(wireless) be set to inside?

- Joey

Community Member

Re: Cisco 1941 Router- IP nat

Joey,

Theoretically you setup is correct.  However it is hard for us to tell you yes or no without seeing your configuration and be able to picture your setup.  What is the ip address on the g0/0?  If you could post ur running config it would be greatful.

Bryan

Community Member

Re: Cisco 1941 Router- IP nat

Joey,

NAT looks like it is configured correctly.  Are you having any issues?

Edit:  Why are you using the route-map to configure NAT?  I may be wrong, but I think you should configure a separate access list.

Bryan

P.S.

For future reference, you should X out ur password "7" keystrings, as they take only a simple google search (or in my case, a simple Ipad App) decode.

Community Member

Re: Cisco 1941 Router- IP nat

Bryan -

Thanks for the assistance. I won't know if I'll have any issues until I send this router to the client, and they connect it to the network.

As for the route-map, I used it only because that was the prior information I was given. I'm still a newbie at this networking stuff, so googled it for proper syntax. (Next time, I won't raise my hand so fast to volunteer to do some networking.)    :O)

And, as for X-ing out my passwd "7" keystrings, I'll google that too, cause I have no idea what that means.

Thanks.

- Joey

Community Member

Re: Cisco 1941 Router- IP nat

Joey,

No problem.  I hope this helped you outl  Just for saftey sake(and frankly, my lack of understanding) I would just create a separate access-list and attach that to the "ip nat source ###" command.  As for the password "7".  When you posted your config, all of the password commands listed under the line commands for "con" and "vty" are easily decrypted.  Just a future reference for you if you need to post a config online like you did here.  As an example:

line con 0

exec-timeout 0 0

password 7

logging synchronous

login local

line aux 0

Replace:

password 7

with:

password 7 xxxxxxxxxxxxxxxxxxxx

Just a heads up for the future.  And I would change your password that you have already configured.

Also, if its not too much of a bother, please mark this question as answered.  Thank you.

Bryan

Cisco Employee

Re: Cisco 1941 Router- IP nat

Hi Bryan,

I haven't had a chance to look at the config (i'm assuming it was removed due to your password warning, which is good).

The reason route-maps are configured is to support a case of load-balancing on multiple outside links, wihch would otherwise cause traffic to blackhole if on ACLs were used. So maybe someone could have mentioned that fact and suggested to use route-maps in advanced so that it's non-disruptive once it's installed and in operation. I used to do that on many cases myself, when setting up new routers.

Community Member

Re: Cisco 1941 Router- IP nat

Gautam,

Im sorry if it came off as if I dont understand Route-maps.  I do.  What I didnt understand was how he was using a route-map with his "ip nat source" command.  Seeing as how when using a route-map for routing load balance, if something falls off the end of the route-map, it will just route normally.  I did not know how that would work with NAT.

Bryan

Cisco Employee

Re: Cisco 1941 Router- IP nat

Hi Bryan,

I apologize, but I'm not sure if that's a question for me, or a statement that you understood what I said about route-map usage in NAT? Do you want me to explain how it works, or have you understood it?

Thanks,

Gautam

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