Stumped - Internet/no Internat

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Just finished a call that complained of no WiFi or Internet. I could plug my laptop into the modem (Cisco w/Charter being the provider) and get great Internet but then plugging that CaT5 into any of three different routers gets nothing. I obviously reset the modem and routers and asked the client to contact Charter for a new modem but what'd I miss? I've never seen those symptoms before. (Anything works great on the Internet when connected directly to the modem, but nothing works through the router. Three separate routers could not verify the Internet was present (no green light and no connections, nothing)).
 
Whose routers were they? (I mean - yours or theirs?) Just asking as, if they're yours, you have presumably been able to test that they are OK when you plug them in elsewhere (i.e another internet connection - in your own office, say)
 
One was their old Netgear router and another a brand new one they bought when they thought their old one failed. The third is an old test router of mine I carry to test for these type of issues. (Tried multiple cables....)
 
Does the modem have a web based UI and can you access that from the LAN side when going through the router?
 
Does the modem have a web based UI and can you access that from the LAN side when going through the router?

I'm not sure. I http'd into each router and checked the details but I didn't try the modem. Usually when it comes to modem issues I have them contact the provider. I did restart and reset (last resort) the modem during my efforts.
 
One was their old Netgear router and another a brand new one they bought when they thought their old one failed. The third is an old test router of mine I carry to test for these type of issues. (Tried multiple cables....)
OK, so chances of all three routers being squiffy and all your cables being duff are pretty much nil. So at least (IMHO) you've narrowed it down to the modem.
 
Did you test both FQDN and IP's? Browsers as well as CLI (ping)? Did you check DNS settings each time on the client?

Not sure I understand your questions (FQDN?) but WiFi works on all of the routers (hence the http sessions I mentioned above) and DHCP works with those routers and the laptop shows corresponding IPs (192.168.X.X) with each router change. When plugged into the modem I obviously am getting the external 75.128.X.X IP and the modem is a Cisco cable modem (no built in WiFi) from Charter. The one thing I can't do which would tell me everything in a minute is a modem swap. I'm getting into a gray area here with a MAC change/registration through Charter which is what their field techs are supposed to be doing for the customer, not me. (Customer has no idea if modem is rented.)
 
Just from what you're saying here my guess is it's a MAC address issue. I'm thinking the MAC has to be registered with Charter. Especially if you know for sure that at least one
of those routers are good.
 
Not sure I understand your questions (FQDN?) but WiFi works on all of the routers (hence the http sessions I mentioned above) and DHCP works with those routers and the laptop shows corresponding IPs (192.168.X.X) with each router change. When plugged into the modem I obviously am getting the external 75.128.X.X IP and the modem is a Cisco cable modem (no built in WiFi) from Charter. The one thing I can't do which would tell me everything in a minute is a modem swap. I'm getting into a gray area here with a MAC change/registration through Charter which is what their field techs are supposed to be doing for the customer, not me. (Customer has no idea if modem is rented.)

FQDN = fully qualified domain name. To use a FQDN, DNS has to work. So if you ping google.com and it fails but if you ping 74.125.21.139 (which is Google's IP) and it works then DNS is not working. Same if you do this in a browser.

If you hooked up your laptop to the modem and it worked and then switched to a router Charter may have not released the MAC binding for the laptop, even if you power cycled the modem. But there should have been lights on the WAN port anyways. Both link light as well as activity light. Which modem?
 
If you hooked up your laptop to the modem and it worked and then switched to a router Charter may have not released the MAC binding for the laptop, even if you power cycled the modem. But there should have been lights on the WAN port anyways. Both link light as well as activity light. Which modem?

It was a Cisco - DPC3008 I think and it showed a solid link light and online light. Plugged into the modem I could browse using DNS (ran speed tests and brought up a few web pages). Like I said, Charter needs to get involved at this point.

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