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New Member

NAT works on router. not for internal host

Hey guys! I'm a 19 year old that has just passed the switching part of the ccnp exam. now i'm preping for the routing part. indoing so i decided to takle NAT. as always....it didn't go so smoothly lol. anyways here is my setup. cisco 2611. internal (inside) address range is 192.168.1.x and external (outside) is DHCP. i specified e0/0 as the outside interface and e0/1 as the inside interface. and applied this ip nat command to the internal interface (e0/1)

IOS ver. 12.2

ip nat inside source list 100 interface Ethernet0/0 overload

this is what access list 100 reads:

access-list 100 permit ip host 192.168.1.1 any

access-list 100 permit ip host 192.168.1.2 any

the ip of e0/1 (the internal int) is 192.168.1.1 with a laptop connected to it via a crossover with an ip of 192.168.1.2. i can initiate an extended ping making the source address that of the internal interface of the router and ping cisco.com and i get a reply. but when i try to ping cisco.com from the laptop it times out. the config of the laptop is 192.168.1.2 mask 255.255.255.0 gateway 192.168.1.1 or that of the int of the router.

ip=192.168.1.2             192.168.1.1                    dhcp

gtwy=192.168.1.1              e0/1              e0/0

[=========]---------------------------[=========]------------------------"the internet"

computer                                          NAT router

                                         ***inside***                                          ***outside***

so to sum up, if i make an extended ping and make the source that of e0/1 and ping cisco.com i get a reply. and i can show NAT is happening by the "sh ip nat translation" command. and i see translation is occuring. if i go to the computer and ping cisco.com i get nothing.

any help, tips, or advice that ends this nightmare will be apreciated greatly!!!!

Mike

1 ACCEPTED SOLUTION

Accepted Solutions

Re: NAT works on router. not for internal host

How is DNS set up on your client ?? I guess this is due to DNS issue. Try pinging the ip of www.cisco.com from Host. That should work.

7 REPLIES

Re: NAT works on router. not for internal host

How is DNS set up on your client ?? I guess this is due to DNS issue. Try pinging the ip of www.cisco.com from Host. That should work.

New Member

Re: NAT works on router. not for internal host

DNS for my external interface is obtained threw my ISP in this case COX. i checked the name servers on the router and i have two records for the two DNS servers my isp uses. as for the computer. i statically assigned the IP of 192.168.1.2 and mask of 255.255.255.0 and the gateway to that of the internal interface of the router (192.168.1.1) and for dns i manually entered that of my isp

New Member

Re: NAT works on router. not for internal host

i can make the router available to anyone on the internet if they would like to telnet into it to take a look. you can contact me online via aim phiberoptik26k or msn mmatteson@inquery.biz

New Member

Re: NAT works on router. not for internal host

Hi Matteson,

You said in your Querry that you are able to ping cisco.com from your router but how can you ping with name from a router...Pl clariy me..

Rgds

nks

Re: NAT works on router. not for internal host

Since his outside ethernet interface is configured for DHCP, his ISP is sending DHCP IP info for his router. THe router gets a leased address. The router points itself to the default gateway specified in the DHCP reply from server, with a default route. (0/0).

I had logged on to his router, and found that, IP routing was not enabled. That was the culprit. The issue is solved. Hope that helps!

Re: NAT works on router. not for internal host

Ooops...i didnt answer your question.... How does router ping www.cisco.com with domainname. DNS information (ip address of his ISP dns servers) are send in the DHCP response to the router. THe router configures itself with those dns server ip addresses. Thats how he is able to ping from the router.

To verify this, give a show host command and you should be seeing the name server ip addresses.

New Member

Re: NAT works on router. not for internal host

I was able to ping cisco.com because the outside interface was obtaining an ip through dhcp and with it came the dns server information. so i was able to use cisco.com instead of their ip.

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