Converting existing DSL-based Airport wireless network to Cable modem

[ChicagoPhil]

I currently have a DSL internet connection (static IP if that matters), and my iMac is connected to the network via an Airport Extreme, but am switching to Comcast Cable for better speed/price.

I picked up the self-install kit from Comcast yesterday and find the included instructions pretty much worthless.

Due to where cable outlets are located, I hope to install the new cable modem in a different room than my computer. However, will I first need to have the computer hard-wired to the Airport to configure the connection? Or should I be able to configure it wirelessly?

If wirelessly, should it be as easy as turning off the computer and Airport, connecting coax from the wall to cable modem, ethernet cable to the Airport, and then powering everything on? Will the iMac instantly recognize the new connection and walk me through configuration?

I am going from a static IP w/ the DSL to, I assume, a dynamic IP with the Cable. Does this further complicate the install?

Thanks for your help,
Phil

 

[khollister]

What DSL HW are you using? Is the AEBS currently set up as the router (NAT), or do you have a DSL modem/router device? We need a little more info on how the AEBS is configured. I believe most cable modems just provide a single public IP (either static or DHCP), and it is completely your responsibility to implement any routing or firewall. If you only have a single device hooked to the network, then routing is optional, although I would still suggest setting up NAT in the AEBS for security, even though your WLAN would only have a single active IP.

 

[ChicagoPhil]

What DSL HW are you using? Is the AEBS currently set up as the router (NAT), or do you have a DSL modem/router device? We need a little more info on how the AEBS is configured. I believe most cable modems just provide a single public IP (either static or DHCP), and it is completely your responsibility to implement any routing or firewall. If you only have a single device hooked to the network, then routing is optional, although I would still suggest setting up NAT in the AEBS for security, even though your WLAN would only have a single active IP.

The Airport is acting as a router, as the only hardware I have from Speakeasy/Covad is the DSL modem.

My connections are: phoneline into modem -> ethernet cable from modem into Airport -> wireless to iMac, PS3, iPhone, windows notebook...

So should all of the devices continue to find and communicate with the Airport after the change to the internet source?

I just need to configure the Airport to speak to the new cable modem, or will it find it automatically?

Thanks again,
Phil

 

[khollister]

If your DSL is static IP, you will need to reconfigure the WAN address of the AEBS to match the new public WAN IP from the cable service. If both were DHCP, it would be plug & play. Since it sounds like you have a NAT wireless LAN, nothing there needs to change. The address range, subnet mask and all should remain the same.

 

[ChicagoPhil]

If your DSL is static IP, you will need to reconfigure the WAN address of the AEBS to match the new public WAN IP from the cable service. If both were DHCP, it would be plug & play. Since it sounds like you have a NAT wireless LAN, nothing there needs to change. The address range, subnet mask and all should remain the same.

Just to be clear, in the case of my static IP internet service, that IP is input to the Airport as it never changes. However in the case of service that uses dynamic IPs, there will be a "fixed" address (the WAN) that is assigned to the cable modem? So this WAN IP should be noted on the cable modem itself?

I assume that I can do this reconfiguration through my iMac connected via wireless, since the LAN will remain intact? Or will I need to temporarily run the cable modem in the same room with the computer so that I can make a wired connection?

Thanks for your help,
Phil

 

[khollister]

OK - let's get a few terms straight. A router has 2 sides, the WAN side (where the ISP connects) and the LAN side. The WAN side will have exactly one IP. This can be a static IP that your ISP assigns, or a dynamic one that is assigned via DHCP from your ISP. In either case, you use Network Address Translation (NAT) to create a "private" LAN that is mapped through to the "public" WAN IP. You can either turn on DHCP in the router to assign a block of private IP's to the LAN devices, or manually set IP's on each LAN device. This has nothing to do with whether your ISP uses static or dynamic IP on the WAN side.

You can configure the airport from the WLAN since there is no reason to change anything on the LAN side. You only need to reconfigure the WAN address.

 

[ChicagoPhil]

Thanks for providing that explanation.

Hopefully this is the last clarifying question:

So on the WAN side, currently I have configured it manually (IP, Subnet, DNS, etc) as provided to me by Speakeasy. Now with Comcast, I will just set to the Airport to DHCP and it will "find" the appropriate IP address and everything should be good to go?

 

[khollister]

Thanks for providing that explanation.

Hopefully this is the last clarifying question:

So on the WAN side, currently I have configured it manually (IP, Subnet, DNS, etc) as provided to me by Speakeasy. Now with Comcast, I will just set to the Airport to DHCP and it will "find" the appropriate IP address and everything should be good to go?

Based on the info you have given me, yes, that's it. Just go into the Internet tab in Airport Utility and change to DHCP, then hit Update.