Need a little router config help

[Sahnik]

Hello folks, I really need some help, I can't get this to work.

Place where I work has SDSL and has a Netopia 7100 router. At the moment we are just using DHCP from the router to get internal IP's, assigning static internal IP's isn't a problem. Problem is I need to get one of the machines an external IP to setup a FTP server. I tried using NAT, but couldn't get it to work. I also tried using 2 network cards in the computer and assigning one of them one of our alloted external IP's (I think).

Anyway, I don't have much experience is the area, so any help would be much appreciated. Here is the info the DSL provider gave us.


NETOPIA ROUTER PRIVATE IP CONFIGURATION
Ethernet IP: 192.168.1.1
Subnet: 255.255.255.0
Usable Ip's: 192.168.1.2-192.168.1.99
DHCP assigned start at 192.168.1.100

NETOPIA ROUTHER PUBLIC STATIC IP CONFIGURATION
Wan IP: xxx.xxx.255.070
Wan Subnet: 255.255.255.192
Wan Default Gateway: xxx.xxx.255.126

Lan IP: xxx.xxx.247.126
Lan Network IP: xxx.xxx.247.120
Lan Subnet: 255.255.255.248
Lan Usable Ip's: xxx.xxx.247.121-xxx.xxx.247.125


When I used NAT I tried sending one of the lan usable ip's to the internal ip address of the computer i wanted the ftp server on, but didn't have any luck at that. I also used one of them with the extra network card and no luck either.


Help! Thanks,
Jim

 

[JustinLerner]

NAT is an address translation scheme to protect internal IP hosts from revealing their actual IP addresses to internet hosts. NAT adds an extra layer of protection to hosts accessing the internet, but may not be desireable for multiple FTP servers, Web servers, etc.

I think you need to configure a separate IP Subnet on your Netopia router (page 9-15, for R7100) for each range of private IP addresses and ISP assigned public IP addresses.

You may also need to read on IP Address Serving and IP Address Pools.

 

[Bglad]

It doesn't look like you have another ip address available to you from the info you gave. If this is not the case and you need another ip address for some readon, you need a switch. Connect the incoming cable to the modem, modem to the switch, and plug the router into the switch. Then plug your FTP machine into the switch, not the router and let it pull its own ip address. You shouldn't have to do this though. In addition, it will leave the FTP machine insecure.

Nat by definition will not work. The purpose of nat is to give out private ip's to your local lan. When a computer sends a request to the internet, the answer comes back and nat knows to send it to the right computer on the lan because it knows which computer requested it. Using FTP, you will have incoming requests and the nat will not know which computer to send it to because there was no request made so it will get thrown out.

You need to open up and forward the FTP port (usually port 21 I think) and manually and permanently direct it to the local LAN ip of the FTP machine. This is done in the setup of the router. You would also want to setup that machine with a static IP instead of DHCP so that it does not change. If it changed, the router would be forwarding the port to the wrong machine on your lan.