Thanks in advance for your help!
After a particularly bone headed move I burned out my old modem. I have purchased a Actiontec modem/router from Best Buy. Its now day 3 of a 15 day return policy.

I use Ethernet to run two laptops off the same system.
I dual booted a windows 7 and Linux mint 18, Sarah, Cinnamon on my dell latitude 6420. The second Laptop is an old Dell Studio 1737 Vista with a Linux Mint Xfce

Windows on both computers configured automatically but as I described in title, the Linux Mint 18, cinnamon on the latitude does not connect to the internet. Now here is the kicker, my old Dell studio/Vista dual boot with Linux mint 18 xcfe stuffed into a flawed teensy weensey hard drive with almost no extra room configure automatically!! I'm saving money to buy a new hard drive to dump it and it out performed my fancy Latitude Linux Mint 18, cinnamon!

I tried dropping the firewall and fooled a little with the Network Connections adding a dsl line but no go.

I tried calling both my ISP and Actiontec service techs which told me they were trained on Windows only and "I have to call the Linux Tech Service." Umm, I think that means you guys.

I am willing to spend time comparing cinnamon to the xcfe but I need help on where to look. I am also willing to look at various Linux online manuals but need to be pointed in the right direction. I am off work tomorrow Friday, 1/13 so will have time to really dig into this and plus, I love to learn.

laptop latitude linux mint 18, Cinnamon
Specs
Dell Latitude E6420 Intel Core
i5-2520M 2.50Ghz 8GB 250GB SSD Win7 Pro 64Bit

Laptop Dell Studio/Linux mint 18, xfce
Specs
Dell studio 1737 64-bit OS
Intel(R) Core (TM)1Dua CPU T6400 @2.GHZ
4.00 GB RAM Mobile Intel (R) 4 series Express Chipset Family
Generic PnP Monitor
9.97 GB of 246 GB

14/Jan/2017 To other Noob who are curious, this solution only relates to linking with a Ethernet cord not wireless. Final solution was reached by deleting password and username under security setting and rebooting my computer.

You say that you have been changing the setup on the laptop and has stopped working.

Its usual for modem/routers to include a firewall - so you probably don't really need one on the laptop.
Have you looked at the router to see what ip addresses it uses,
e.g. If the router has an address of 192.168.1.1 then PC's can use addresses in the range 192.168.1.2 - 192.168.1.254.
Try entering the command below and copying the output to the forumHope to see something roughly like

I couldn't cut and paste because I can't get online but I copied your message and changed what was different. Gosh what big numbers you have Jeremy!

eth0 Link encap:Ethernet HWaddr 5c:26:0a:88:d0:f9
UP BROADCAST RUNNING MULTICAST MTU:1500 Metrical
RX packets:3 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:573(573.0 MiB) TX bytes:0 (0.0B)
Interrupt:20 Memory:e2e00000-e2e20000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:376 errors:0 dropped:0 overruns:0 frame:0
TX packets:376 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1
RX bytes:30240 (30.2 KB) TX bytes:30240 (30.2 KB)

The eth0 is your ethernet connection.indicates that you have a running connection.
RX packets:3 RX bytes:573(573.0 MiB) TX bytes:0 (0.0B) - should this be RX bytes:573(573.0B) ?

The tiny amount of data coming down the wire seems to indicate that physically everything is OK.
I suggest you try booting from USB or DVD a copy of your favourite "live" distro.
This ought to detect everything automatically and test a web browser.

Linux allows you to configure so many aspects of networking that it may be simpler to do a quick reinstall of your distro (depending on how much configuration, customisation etc you have done). But try the "live" distro first.

Hello,
As JeremyBoden stated, it looks like your ethernet interface is up. However, It does NOT appear to have obtained an ip address from your router. Notice the "inet" and "inet6" fields in your loopback device are missing on your ethernet.

You might try or dhclient if dhcpcd does not work. Then again type (or "ip a") and look for an inet addresss under eth0

Hi Jeremy
Just to be clear this dell Latitude with cinnamon has never been able to get online since I have changed to my new modem/router. Three other OS (2 x Windows and 1 x LM) configured automatically.

Also to be clear I am trying to establish a Ethernet cable connection. I have not even attempted wireless. It would seem to me that LM cinnamon is blocking a connection.

Currently the line you questioned reads slightly differently
RX bytes 909440 (909.0 KB) TX bytes:909440 (909.4 KB)

All of the numbers are larger now. Instead of 573(573.0 MiB) it is now RX bytes: 126065 (126.0 KB)but alas no connection.

I tried to run a live DVD but it hung up. I'd rather try poking around before I go for a reinstall but that would be my next viable final solution.
I am looking at easytipsproject.com I put in iwconfig and this came up
wlp2s0 IEEE 802.llabgn ESSID:Off/any
Mode: Managed Access Point: Not-Associated Tx-Power=Off
Retry short limit:7 RTS thrff Fragment thrff
Power Managementff
enol No wireless extentions
lo No wireless extentions

in terminal window I put rfkill list all and got
0: dell-wifi: wireless LAN
Soft blocked:no
hard blocked: yes
1: phy0: Wireless LAN
soft blocked: no
hard blocked: yes
hmmmm

Hard block is generally due to a physical switch that can enable/disable a wireless connection. But as you said you are trying to connect via ethernet, this should not be your problem

Helllo The Ezekiel Project
I tried putting in dhcpcd eth0 and got
The program 'dhcpcd' is currently not intalled. You can install it by typing:sudo apt install dhcpcd5
I got
Reading package lists...done
Building dependency tree
Reading state information... done
E; unable to locate package dhcpcd5

I am a noob but would this mean I am missing a driver? how about just updating drivers?

You won't necessarily have dhcpcd installed. Try if you haven't already.
If you have neither dhclient or dhcpcd installed, try or and see if it can find either package in the repositories

Hello The ezekiel project
tried first suggestion dhclient eh0 and got
Cannot find device eth0
is that last letter O or 0 i used zero

tried apt-cache search dhcpcd and got
dhcpcd-bus - DBus bindings for dhcpcd
dhcpcd-gtk GTK+ frontend for dhcpcd and wpa supplicant
dhcpcd5 - DHCPv4, IPv6RA and DHCPv6 client with IPv4all support

Yes, that is a zero. Strange that it says it can't find it. It looks like dhcpcd5 is the one you want. I would try to install that and try again

erm sorry how do I install a dhcpcd5 and briefly what is it?

It's a dhcp client. It's responsible for getting you an ip address from your network. You can read more about it here

Hi T.E.P.
Tried what you suggested and got
E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied)
E: Unable to lock the administration directory (/var/lib/dpkg/), Are you root?