Conflicting DHCP range on AirPort extreme

[vboston]

How do I correcting the conflict with my DHCP and Nat on AirPort. Comcast couldn't fix the problem.

 

[Fishrrman]

You're not providing enough information...

 

[campyguy]

Wasted my time here. NM.

 

[vboston]

Hi macrumors community. I need some help. Comcast upgraded my modem and now I'm unable to connect my AirPort extreme. Even with Comcast's help I still get a DHCP and NAT conflict. They tried to fix on their end but to no avail. How do fix this issue? Thank you

 

[Fishrrman]

Is the Comcast modem a modem ONLY?
Or... is it a combined "residential gateway" (modem and router in one unit)?
A residential gateway has 4 "LAN" ethernet ports on the back.
A "modem only" will probably have just ONE ethernet port.

If it's a residential gateway (with router built in), I'd do this:
- Set up the Airport Extreme in "bridge mode" and let the Comcast router do routing functions. I've done this with my own (old) AE for almost 8 years now, runs fine that way.

 

[vboston]

Is the Comcast modem a modem ONLY?
Or... is it a combined "residential gateway" (modem and router in one unit)?
A residential gateway has 4 "LAN" ethernet ports on the back.
A "modem only" will probably have just ONE ethernet port.

If it's a residential gateway (with router built in), I'd do this:
- Set up the Airport Extreme in "bridge mode" and let the Comcast router do routing functions. I've done this with my own (old) AE for almost 8 years now, runs fine that way.

[doublepost=1531186830][/doublepost]thank you Fishrrman. Now how do I do that exactly? I'm not very good at setting things up without hours of researching.

 

[Fishrrman]

1. Open Airport Utility
2. Click the icon for your base station and enter wifi password if asked
3. Hover cursor over icon for base station, popup window appears with your stats.
4. Click the "edit" button, lower right of popup
5. Starting on the left, work your way through the panels, to be sure things are as you like them.
6. When you get to the "network" panel, where it says "router mode", select "off" (bridge mode)
7. Down at the bottom, click the update button. It will take a couple of minutes for the Airport to make the changes and reboot.

When it reboots, you should be as follows:
- Router, NAT, DHCP all from the Comcast modem/router
- Wireless from the Airport Extreme -- ONLY wifi, the other functions are being handled by the routing functions of the residential gateway.

The other thing you need to do is "find your way" into the Comcast gateway, and TURN OFF its wifi.
DO NOT try to disable routing.
You want the gateway to work as if it were a "wired only" router, and the wireless functions will be handled by the AE.

 

[MBAir2010]

1. Open Airport Utility
2. Click the icon for your base station and enter wifi password if asked
3. Hover cursor over icon for base station, popup window appears with your stats.
4. Click the "edit" button, lower right of popup
5. Starting on the left, work your way through the panels, to be sure things are as you like them.
6. When you get to the "network" panel, where it says "router mode", select "off" (bridge mode)
7. Down at the bottom, click the update button. It will take a couple of minutes for the Airport to make the changes and reboot.

When it reboots, you should be as follows:
- Router, NAT, DHCP all from the Comcast modem/router
- Wireless from the Airport Extreme -- ONLY wifi, the other functions are being handled by the routing functions of the residential gateway.

The other thing you need to do is "find your way" into the Comcast gateway, and TURN OFF its wifi.
DO NOT try to disable routing.
You want the gateway to work as if it were a "wired only" router, and the wireless functions will be handled by the AE.

Bravo Fish!
This reply is to the point, extremely helpful and mature.
I hope the thread starter appreciates your advice.