Disable Option for DHCP

[drdavedmin]

From reading posts, it seems the best option for me, with an Apple Time Capsule, is to configure the Time Capsule (router) with a static IP address and put it in the Omma telo hub's DMZ. This assumes the Ooma is placed directily after the modem and before the Time Capsule router.

My question is what to put in the settings for the Time Capsule using the AirPort Utility (Internet - TCP/IP - Configure IPv4 Manually. Which setting there gets the static IP within the Oomas numbering range (172...) ??

Specifically, how do I set each of these choices:
Ip Address
Subnet Mask
Router Address
DNS Server(s)
Domain Name

All except the DNS Servers are automatically filled in when I change the Configure IPv4 from "Using DHCP" to "Manually."
Again, which is the Time Capsule static IP setting, and do the others stay the same? And if Comcast changes any of these other settings, what then?

[murphy]

Forget static IP configuration.
It's more trouble than it is worth unless you are a networking expert.

Set the start and end IP addresses in the Ooma DHCP table to 172.27.35.2.
Set the DMZ value in the Ooma to 172.27.35.2.
Leave the Apple in DHCP mode.
Since there is only one address in the DHCP table, the Apple will always get that address.

[drdavedmin]

Thanks for the ideas. In my case setting a single IP address in the Ooma DHCP settings, and the same address in the DMZ (for the Apple router) resulted in error messages in the Apple router, about having a double NAT system. While I was able to bypass it and have the Apple router assign IP addresses, surfing the Internet or doing email were all blocked. When I attempted to open a web page, I got the Comcast activation screen. Since this did not happen when I connected my computer directly to the Comcast router.

I finally gave up and did a hard reset on the Apple router, re-established my settings, and placed the Ooma after the Apple router. I believe this means that I cannot benefit from the QOS capabilities of the Ooma Telo, but at least it doesn't take down my network. I don't believe the Apple router is capable of setting up QOS for a particular device.

Is this likely a problem created because the Apple router needed a reset for some other reason? How do others handle the double NAT error? Would assigning the router a static IP eliminate this problem?

Would appreciate any assistance!

[murphy]

Double NAT is not a problem.
It's safer than single NAT.
Apparently the Apple router thinks that it is a problem.
Can you configure the Apple router to ignore what it thinks is an error?

[drdavedmin]

I think I remembered this wrong.......... I believe the problem was having two DHCP systems

[scottlindner]

I think I remembered this wrong.......... I believe the problem was having two DHCP systems

If you set it up as a double NAT, you will have two LANs each with their own subnet so there should be no double DHCP issue. If you put both LANs on the same subnet, well.. I dunno what routers do in that case but it's possible that could be the cause of the problems.

Here's what I mean.
Cable/DSL modem LAN 192.168.1/24
wireless router LAN 192.168.2/24

If you make sure you use different subnets for each LAN, you shouldn't be having issues with two DHCP servers even if you do have two DHCP servers.

Cheers,
Scott

[nn5i]

If you make sure you use different subnets for each LAN, you shouldn't be having issues with two DHCP servers even if you do have two DHCP servers.

Cheers,
Scott

Not necessarily true. A DHCP request goes to every host; if more than one DHCP server responds to the same request, chaos results. Subnet isolation can avoid this, but in many routers subnet isolation must be specifically set up. In some routers this is complicated to do, and in some other routers it can't be done at all.

[scottlindner]

If you make sure you use different subnets for each LAN, you shouldn't be having issues with two DHCP servers even if you do have two DHCP servers.

Cheers,
Scott

Not necessarily true. A DHCP request goes to every host; if more than one DHCP server responds to the same request, chaos results. Subnet isolation can avoid this, but in many routers subnet isolation must be specifically set up. In some routers this is complicated to do, and in some other routers it can't be done at all.

It works fine for me this way and I have five devices with DHCP servers. As long as I have them on different subnets, I have no issues.

I will ask the network guys at work to confirm. This is fairly trivial stuff.

Scott

[drdavedmin]

You have been very helpful and I really appreciate it. The subnet thing you mention is very likely the problem. My router was already using the 172. series of IP addresses, which the Ooma also uses. I can reset my router to use a 10. series or a 192. series. Would that be likely to cure the issue?

[scottlindner]

You have been very helpful and I really appreciate it. The subnet thing you mention is very likely the problem. My router was already using the 172. series of IP addresses, which the Ooma also uses. I can reset my router to use a 10. series or a 192. series. Would that be likely to cure the issue?

I suspect it will, but you don't have to change up the Class A, B and C subnets to achieve what you want. I don't have time to explain it right now, but there are a lot of ways to address this. I typically use 192.168.x/24 for all of my LANs and just change the "x" to be different. The net mask denoted by "/24" tells me that it will be a different subnet. I picked mine to go along with the default subnet of certain devices so I can reset them and not have to worry about using a laptop and a short network cable to reset it to the subnet that I want. If that doesn't make sense, don't worry about it.

Scott