Using 2611 as Gateway with Cable Modem and NAT

[blobmeister]

OK I have had enough, I admit defeat!!! I have got a 2611 and am trying to get it to act as a Gateway onto the internet for my 3 PC's in the house. I have played about with setting up NAT and cannot get it to work!! I really need somebody to give me the commands (explanations would be good too!) to get it to work, as the missus is getting pist at me cutting her Internet connectivity so I can try and get it to work!
Anyway here is what I need, any help would be really really appreciated.
I want e0/0 to have DHCP (cable modem is DHCP Server) and obviously this is the internet port. Port e0/1 will have a static ip of 192.168.1.5 and this is obviously the LAN side of the network.
I have 3 PC's in the internal lan on 192.168.1.0/25 subnet and I would like any IP's in this range to be NAT'd to the internet.
So come on folks I am sure that one of you CISCO Guru's must know what to do.

Thanks for any help

Craig Jameson

 

[dredoggg]

how far have you gotten so far???
lets see your config

 

[rburke]

Here is my working config on a 2514 with IOS 12.2. I've tried to modify it to work on the 2611. Let me know if this helps or if you have any other questions.

CONFIG:
version 12.2
no service single-slot-reload-enable
service timestamps debug uptime
service timestamps log uptime
service password-encryption
!
hostname p.gateway
!
enable secret 5 xxxxxxxx
!
ip subnet-zero
no ip finger
ip name-server <ISP DNS #1>
ip name-server <ISP DNS #2>
ip dhcp excluded-address 192.168.1.5
!
ip dhcp pool HOME
network 192.168.1.0 255.255.255.0
default-router 192.168.1.5
dns-server <ISP DNS #1> <ISP DNS #2>
lease 0 2 <- 2 hour lease of IP
!
!
!
!
interface Ethernet0/0
mac-address xxxx.xxxx.xxxx <- cloning a MAC address
ip address dhcp
ip nat outside
no cdp enable
!
interface Ethernet0/1
ip address 192.168.1.5 255.255.255.0
ip nat inside
!
interface Serial0
no ip address
shutdown
no fair-queue
!
interface Serial1
no ip address
shutdown
!
ip nat inside source list 1 interface Ethernet0/0 overload
!
ip classless
ip route 0.0.0.0 0.0.0.0 Ethernet0/0
no ip http server
!
access-list 1 permit any
!
line con 0
exec-timeout 60 0
logging synchronous
transport input none
line aux 0
line vty 0 4
password 7 xxxxxxxx
login local
!
end



Burke

 

[gaveeve]

I read about this on this forum a while back. Its called 'NAT on a stick'. It is specifically designed to get more addresses from your cable connection (not legal in my neck of the woods). The link is

http://www.cisco.com/warp/public/556/nat-on-stick.html.

On your config you have dns servers. That seems unecessarily complicated.
This uses your cable modem as the interface and uses the router to nat the other pc's. good luck.

 

[dredoggg]

These are the only two 'ip nat' lines that I have (except for inside & outside on each interface)

ip nat pool COMPANYNAME-natpool-258 MY-PUB-IP MY-PUB-IP netmask 255.255.255.0

ip nat inside source list 1 pool COMPANYNAME-natpool-258 overload

MY-PUB-IP is replaced with, you guessed it, a public IP... That is the IP the world sees us as. If for the second MY-PUB-IP I put a higher IP on my block, then the public would see a range of IPs.

oops, just went back and read your original post again.
maybe gaveeve's post helps... I didn't realize you were dhcp'ing your pub ip... But, maybe my two lines will help the lightbulb go off above your head if the other post doesn't...

sorry, good luck.

 

[mylchreest]

I'm probably wrong but isn't 192.168.1.0/25 an illegal subnetting (255.255.255.128 on a class C address means that the single subnetting bit in the fourth octet wil be always on or off)

 

[blobmeister]

Thanks for all your help guys. I have now managed to get it working!!!

One other problem I am seeing is if I reboot the Router it does not seem to load the running config automatically, is this normal? If I do copy start run then it works OK.

Thanks again for all your help.

 

[shawnpd40]

How is your router booting? What is the value of your config-register? If the value is 0x102 thru 0x10F the routr should boot from NVRAM...if the config-reg value is 0x101 then it is booting from ROM...I think! Good luck let us know!

 

[blobmeister]

OK 3 questions,

How do I find out what the config-reg is set to
and 2
How do I do a Static mapping
and 3
Does anybody have any idea if it will allow me to do DCC transfers on irc?

 

[shawnpd40]

The show ver command will display the what the config-reg is set to.

Do you mean a static route? The syntax for a static route is ip route network mask address|interface distance

Hope this helps!

 

[blobmeister]

Thanks for the info on the config reg. I had set it to 2142 to get the old password and forgot to change it back.
My mistake also because I want to know how to do a PORT MAPPING.