Swapped Modems, same model, static WAN IP, Router couldn't reconnect

videobruce · Post by **videobruce** » Tue Nov 21, 2017 10:51 am

No Firewall in Router or in O/S
Static IP addresses for all my devices except for a ATA (Obi202)
Nothing special or fancy in the LAN.
All wired except for a Laptop.

Long story short, I swapped identical Modems that gave a static WAN IP address (yes it was static!) Both had a RF connection, new one showed connected. I moved the Router cable to the new modem with no reboot of the Router.

No connection to the Internet. I rebooted the Router, still nothing. I then noted there was IP assigned. I did a DHCP release and renew twice. Still nothing.

I then reset the Router (which I didn't want to do), still nothing. No WAN IP assigned still.
I changed the LAN start IP adress from 100 to 2 since I use static IP address and after a minute the Router finally received a WAN IP address.

Questions;
1. Going from one identical Modem to another that passes an IDENTICAL IP address to the Router, is it still necessary to reboot the Router?
2. Even after rebooting, why wasn't there connectivity between the Modem & Router, even thou the Modem 'Link' LED showed connected and with activity?
3. After the Router reset, is spite of the LAN starting address at 100 which was outside of the static IP's of my devices, why didn't the Router get the WAN address from the Modem??

Win7
Spectrum ISP
Zoom 5341J Modem
TP-Link WDR-3600 Router running dd-wrt firmware

Post by **YeOldeStonecat** » Tue Nov 21, 2017 4:16 pm

Did you get this modem from your ISP? If not, did you call your ISP to have them provision it?

videobruce · Post by **videobruce** » Tue Nov 21, 2017 5:31 pm

No and yes of course.

One thing (other than your question) is when the new Modem was provisioned/authorized, the Router was not connected at the time since I have VoIP and I wouldn't of been able to make the call in the 1st place. (no toy phone here).
I have done a swap before with no issue, same setup. Different other Modem, but both had RF connected.

YARDofSTUF · Post by **YARDofSTUF** » Wed Nov 22, 2017 3:15 pm

I would unplug the modem and power it back on so that it tries to connect while hooked up to your router, comcast seems to like it being that way so it sees the routers MAC address.

videobruce · Post by **videobruce** » Wed Nov 22, 2017 5:22 pm

The new Modem was powered on. It was not connected to the Router or a PC.
The old Modem was still connected to the Router.
Except for the 'Link" light, all four indicators were lit in a normal/active state making one think it was already activated.
I called gave him the MAC address, he activated it, I watched the lights cycle, the call was disconnected (I have VoIP and was using that for the call).
I moved the Router cable from the old to the new, NOT rebooting the Modem (purposely), checked for Internet access, but nothing.
Rebooted the Router, still nothing, rebooted everything, still nothing.

Off time was 20-30 seconds.

I eventually got things back, but never had this problem before after 5 or 6 other swaps throughout the years.