Leaving Static IP's and Entering DHCP with AD 1

[targaco]

Here is my situation...

I have DSL service where I have 16 IP addresses. I am also running Active Directory on Win2K server. I want to dump my DSL connection and utilize the Cable connection we have just installed in our office. The Cable connection does not have a "static" IP.

How would you approach converting our netword with AD to the new cable dynamic IP running DHCP?

Win2K Server w/Active Directory
SonicWall SOHO 10
Cisco Catalyst 2650-24
RCA DCM305 Cable Modem

 

[ricpinto]

I will be amaze if somebody can do it. Is your ISP for Cable modem doesn't offer static IPs?

 

[FaiTHLeSS]

If you have a router running you would just let that deal with the IP change on the cable connection side, then setup a private network using 192.168.*.* range with NAT running. The router would have 2ips, the external IP from the cable ISP and an internal one. I also take it your not running any internet facing services like web server or ftp server? But you could also keep both connections in your office and have some sort of backup, so if one connection where to go down you could fall over to the other.

 

[GlenJohnson]

So you're paying for 16 ip addresses? If this is correct, what is the need? Thanks.

Glen A. Johnson
"To fear the worst oft cures the worse."
William Shakespeare (1564-1616); English dramatist, poet.

Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884

 

[ricpinto]

Now I get the picture because I assumed that you host your email, website and other services requiring you to have a fixed ip address. If you have this services or users that need a fixed ip address then you can't used the cable modem other than that you can do it by making sure your Cisco router supports NAT as FaiTHLeSS already summarized.

 

[targaco]

No static IP's from the cable modem. I've been told that they change, but don't change that often. Famous last words. I called Comcast and they don't offer a static IP service in my area so this is what I'm stuck with.

As to why I'm paying for 16 IP's. When I first signed up with my DSL service, 16 IP's were offered with the package. Now it's just a matter of convience why I don't change.

Looks like I'll use a Netopia router I have sitting around to go between the cable modem and LAN for the solution FaiTHLeSS provided.

With my limited knowledge of such subjects, the way I see this coming together is the Netopia router running DHCP to the internet to handle the IP address changes of the Cable service and NAT to the LAN for the AD server and all other pieces of the network. I'm 99% sure the Cisco Switch supports NAT. I'm sure the Netopia does NAT too, though I don't know about the DHCP protocol required for the connection to the internet.

 

[targaco]

Just for clairification, I have a Cisco 2950 Switch.

 

[ricpinto]

It seems like SonicWall SOHO 10 supports DHCP and NAT then you might as well use it to ease the processor of your server.

Internet->cable modem->router ->firewall/NAT/dhcp->switch->LAN

The tricky part is the configuration of the firewall, you have to enter an ip address in your server similar to the default subnet of the firewall. Then enter the default ip address of the firewall in your server's IExlorer and configure the scope of your DHCP and make sure NAT is enabled.

 

[FaiTHLeSS]

I think you will have todo it

inet> cablemodem > router/nat > firewall/dhcp > switch > lan

Since you only have 1 IP.

NAT traffic to switches just looks like any other traffic so no need to worry about the switch.

I would let the router carry out the nat'ing.

 

[ricpinto]

FaiTHleSS:
I agree with you and that's the best config. but I have also experience that my Cisco router when I requested for NAT feature they are making me pay for it. "You want extra feature for your router, pay for it".

 

[FaiTHLeSS]

Hmm ok, but i think if set it up as

router > firewall/nat/dhcp > switch > lan

You would have to make the router transparent as you will only have 1IP and give the IP to the nat'ing device ?

What router do you have?

 

[ricpinto]

Opps, I blunder again, I missed your point.. must be the booze last night from pub when I made my post. One ip definitely is a no go for my diagram. For my case it works because I have 16 public IP's.

 

[FaiTHLeSS]

heh no problem, so much easier doing networking with multiple public static ips than it is with nat.