Why would I get a private address through DHCP on the WAN?

Internet went down last night, narrowed it down to the ISP, decided to release the IP address and renew on the WAN interface and I got 192.168.100.10.

Is there any possible explanation for this? I wouldn't ever expect to see a private address on the WAN. Perhaps the modem is programmed to default to that if it can't connect to a DHCP server on the ISP's side?

What brand of modem do you have? I know that with the Motorola cable modems, their internal address is 192.168.100.1, and will sometimes when there is a dhcp issue will assign an address from it's internal pool, usually this is turned off by the provider, but during an outage it can still assign one of those out.

It's a Cisco DPC3010.

Your explanation makes sense, I'm betting on that as the cause.

Admiral Akmir said:

It's a linksys DPC3010.

Your explanation makes sense, I'm betting on that as the cause.

Click to expand...

Corrected
I used to work for an ISP on the edge of civilization.
To get on line north of us we could provide a point to point Line of sight microwave link, we even had a broadcast licence.

We gave customers a private IP, gateway-ed through us.

10 years on the internet is full & many cheep ISPs actually don't have enough IPs for customers and use a nasty mess call carrier grade nat.