My new AC2600 won't connect to the internet, but my old Linksys will.

[blkcffee]

Title. Everything else will connect, but I can't seem to get a connection through to the internet. Help! I've already tryed power cycling and resetting the router.

[Kitsap]

Additional information is required before this can be sorted out.

What is the brand name and model number of the modem/gateway you are connecting your router to?

Are the devices you are connecting to the router going through an ethernet cable or wi-fi or both?

What are these devices?

[plemans]

@Kitsap is correct. Details are needed and key. 

Especially what modem/gateway you're connected to. 

Some routers play nicer with double nats than netgear devices do. 

A double nat happens when you cascade more than 1 router.
https://kb.netgear.com/30186/What-is-Double-NAT
Fixes if you're in a double nat? There’s 3 options but only use 1.
1. Put the modem/gateway in modem only/pass through mode. This disables its routing functions.
2. Leave the modem/gateway in router mode but put the Netgears IP address into its DMZ. This forwards the data to the netgear. You can either leave the modem/gateway’s wireless enabled or disabled. Just make sure its using a different wifi channel to prevent interference
3. Put the Netgear into access point mode. This disables its routing functions. Wifi/ethernet still works but it does disable some features.
https://kb.netgear.com/26765/Which-features-are-disabled-on-my-NETGEAR-router-when-it-is-set-to-AP-M...

[blkcffee]

Alright- I'm going to have one device running through an Ethernet cable and about 5 on wireless. Not sure about this model of the modem but here's some pics.

[plemans]

Holy cow. 

Thats an old docsis 2.0 modem.

I'm impressed your ISP is even letting you use it as most have transitioned fully to docsis 3.0 and some are pushing docsis 3.1 right now. 

http://www.cablemodems.com/downloads/specsheets/U10C018_DatasheetPDF7.pdf

[Kitsap]

@blkcffee   

You may struggle with that old modem.  I am also surprised the ISP allows it to connect to their system.

May I ask who is your internet service provider (ISP) and what part of the world you are located?

With your existing equipment, the first option is to power down (pull the power cord) for both the modem and the router.

Make sure the coax is connected to your modem and power it up.  Allow plenty of time for the modem to boot and stabilize.

Connect the router to the modem via ethernet cable and power up the router.  Allow plenty of time for the router to boot and stabilize.

Check to see if you have an internet connection via either wi-fi or ethernet.

[blkcffee]

Alright, it didn't work. I can connect to the network, but no internet. (Same as before) The Ethernet cable light and the 2.4g lights are flashing. The internet light is orange. I live in upstate NY and I have spectrum. I believe we got this modem around ~2013? Not 100% sure.

[Kitsap]

Your modem has a 100 Mbps ethernet interface.  Your internet LED will be orange to indicate the 100 Mbps connection.

One option for an easy test is to power up the modem and router in the opposite sequence from above.

Have you been using the same patch cables that you are sure are good?

I would suggest it is time to consider replacing the modem.  What is the capacity of the service plan you buy from Spectrum? 

[plemans]

Even though that device has a 100mbps interface, its only rated at up to 42mbps. Most spectrum plans start a lot faster than that. 

I'd be checking into a new modem from spectrum. I'm actually pretty impressed they even allowed you to keep using it. They did a push almost 5 years ago to phase out docsis 2.0 devices. 

I'd contact spectrum.