Please help review 1605R config questions.

[cventicinque]

Hi,

I have a 1605R that I want to use to share out my cable modem connection. I have a Linksys Broadband router that is doing the job now but, I want to learn more about cisco so I am undertaking this little project. I would just like to go over my plan with you guys to make sure I am heading in the right direction as I have no "real world" experience and this will be my first time configuring a router from scratch outside of a classroom. Here it goes:

I know I have to set 1 interface with a public IP adress and the other with a private address for use on my home LAN. All of the computers on the LAN will have to have an address on the same subnet as this interface. The public interface will be assigned by my ISP via DHCP, my ISP does not offer static addressing. I am running IOS ver. 12.1(5)T10 so I know the command to do this is "ip address dhcp". I know that I then must configure the router to share out this address. The question is, do I use NAT or PAT? I think you use NAT when you have a pool (several) of public IP addresses and you use PAT when you only have 1 public IP address. Is this correct?

Also, can I configure NAT or PAT when the public IP address is assigned via DHCP? Is there a problem with the fact that I am not able to "hard-code" the interface with an IP address?

And finally, I don't think I need to configure the router to act as a DHCP server for my LAN, correct? As long as I assign the PCs IP addresses that are on the same IP subnet, this should work, right?

Thanks for your help, Chris

[MickPhelps]

1) You don't need to configure DHCP on your router for your host machines. Assign them 192.168.1.x addresses.

2) I don't know if DHCP and PAT will work together, but the syntax for PAT is:

ip nat inside source list 10 interface ethernet0 overload

access-list 10 permit 192.168.1.0 0.0.0.255

interface ethernet0

ip nat outside

!

interface ethernet1

ip nat inside

!

You were correct in your assumptions about PAT vs NAT. The downside here is that people won't be able to connect to you with applications like Netmeeting.

Mick.

[cventicinque]

I have netmeeting working on one of my PCs with the linksys router by forwarding the ports that netmeeting uses to that pc, the 1605 dosen't have similar functionality?

[MickPhelps]

Yes, the syntax is:

ip nat inside source static tcp (port) 192.168.1.1 (port) 204.x.x.x extendable(?)

I'm pretty sure that's the right sytax, but you may want to "?" it out.

Mick.

[cventicinque]

I will try it out when I get home, thank you very much for the help.

Regards, Chris

[saridder]

The router can be a DHCP server for hosts inside your LAN, but it would have to be off of your internal interface. As for the NAT, try using the command ip nat inside source (external int) as reference point. This may take care of the fact that you don't know what the natted address will be because of the DHCP asigned address on the int.

Use PAT.