Strange IP address assignment

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Haole Boy

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Aloha everyone. Would like some feedback on a strange situation I ran across. I bought a new router last year (D-Link DSR-250) and am finally starting to use it. Since I knew it has been sitting for a while, the first order of business is to update the firmware. I connect the router to my laptop and find the appropriate D-Link page to download the various firmware updates (there are several to put on). So far, so good.

Put on the first update, router reboots, and I cannot connect to it! Run ipconfig, I get this:

Ethernet adapter Ethernet:

Connection-specific DNS Suffix . :
IPv4 Address. . . . . . . . . . . : 72.253.163.247
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 72.253.163.1

What??? It was 192.168.10.x. And yes, DHCP on the router is turned on. An 'ipconfig /renew' resolved the situation, but I'm trying to understand where the 72.253.1636.x came from?? The ethernet card is identified as Realtek PCIe GBE Family Controller and the machine is a Lenovo ideaPad Flex4-1570.

Thanx!

Harry Z
 
The router passed the public IP to you. Might have been an undocumented feature during the reboot process. I've seen things like that happen before. Not common but it does happen. I'd revisit all the settings to make sure that it's not in bridge mode which might cause the router to ignore the DHCP server and pass the public IP to the endpoint.
 
I'm with Mark....timing was right...no...timing was wrong, just an odd window where the router was very briefly bridged during the reboot process....before it fully booted up and had NAT running with internal DHCP. After you experienced that, unplugging your laptops ETH cable and plugging back in (or just doing IPCONFIG /RENEW at the prompt)....would have brought back the private class C subnet.
 
OK, just trying to learn here... not trying to be argumentative....

My public IP is 141.239.216.xxx, so that's not it.

Also, the D-Link is "downstream" (is that the correct term?) from the HawaiianTel router / gateway and that has DHCP enabled and dishes out 192.168.200.xxx addresses.

So, anyone have another explanation for the 72.253.163.1 address?

Also, D-Link was not a preference, but it was the only residential class router I could find with 8 ports. I had my house re-wired with Cat-6 and RG-6 coax to every room.

Mahalo for your assistance!

Harry Z
 
Do you have a static IP address on your internet service? Your Dlink would have by default requested an IP address, and If your modem/router from the ISP was on passthrough it would get a direct dynamic public address. That would be different that your static IP that is assigned. Might have just been passthrough while the router booted.
 
Haole Boy said:
OK, just trying to learn here... not trying to be argumentative....

My public IP is 141.239.216.xxx, so that's not it.

Also, the D-Link is "downstream" (is that the correct term?) from the HawaiianTel router / gateway and that has DHCP enabled and dishes out 192.168.200.xxx addresses.

So, anyone have another explanation for the 72.253.163.1 address?

Also, D-Link was not a preference, but it was the only residential class router I could find with 8 ports. I had my house re-wired with Cat-6 and RG-6 coax to every room.

Mahalo for your assistance!

Harry Z
Click to expand...
Ok the 141 addresses are also Hawian Telecom IPs. Lots of Telcoms have more than one subnet of ranges to handout. It may be as simple as your old IP subnet was full so they handed you a new one.

You shouldn't attach the D-Link router to a router that is already providing DHCP as it sounds like you are setting up a double or nested NAT structure which can cause problems. It does sound like for a moment your D-Link was seeing directly the outside world. Is perhaps NAT turned OFF on the modem so that all of your devices connected to the modem are bridged directly to the internet? (!!!) If you already have a modem/router and you are NOT bridging the device I don't see what the D-Link is supposed to do for you.
 
I was going through initial setup / updating of the D-Link, so it was attached to the HawaiianTel router so that I could download all the firmware updates for the D-Link to the laptop connected to the D-Link. The HawaiianTel router is currently the DHCP server for my LAN, so there is no reason I can think of for the D-Link having that HT address. Very confusing.

Also, I run double NAT for my 'bench' machine and all customer machines that get connected in my house. No problems, and I've read on here that other folks have done this also.

Mahalo,

Harry Z
 
Haole Boy said:
My public IP is 141.239.216.xxx, so that's not it.
Click to expand...
So is this a fixed IP address? In other words is your account provisioned for a fixed IP, business, versus DHCP, consumer. What you're describing happens often with a service provisioned with a fixed IP.

ISP account - provisioned for X fixed IP's
ISP modem - provisioned for the gateway address for the provisioned fixed IP's. Now comes something extra that I see fairly often. The ISP leaves WAN DHCP, totally separate from LAN, turned on even if there's a fixed IP. In the case of Comcast you can log into the cable modem, look at the Internet properties and you'll see both fixed IP and DHCP IP gateways if they leave DHCP WAN on. That's one way I can tell if the ISP is fixed or DHCP with out calling the ISP.

During the reboot process the WAN often comes up before the LAN so WAN is handing handing out a public DHCP. I used to know how to look up whether a public IP was from an ISP DHCP pool or fixed but that eludes me for the time being.
 
Not a fixed IP address from my ISP. I don't see any indication of when I last received a new external IP address, but it's been 8 days since the last reboot.
 
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