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Troubleshooting Internet Connection

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Last Modified: 2012-06-22
Setup:  Ethernet cable from Internet modem to a switch
             Cable from switch to firewall
             Cable from Firewall to Lan switch

I want to test the internet connection outside of the network so I'm trying to hook my laptop to the first switch but I get nothing.  The laptop is set for DHCP.  I have done the ipconfig commands /release, /renew, /flush dns.  When I look at the properties of the connections it is sending and receiving packets but I can't bring up a browser page.  What am I doing wrong???
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Commented:
There are a few things to consider here:

Since you are connecting directly to the modem, you might need to connect through PPPoE or other tunneling protocol.

Your ISP can easily only allow one IP address to be assigned to the devices beyond your modem, and since your firewall is already using it, your laptop wont get anything from DHCP.
larry urbanDevOps Engineer

Commented:
Is your firewall a NAT? if so it is either your DHCP server or you have a proxy setting in your browser that you don't need when not behind the firewall.

Author

Commented:
tomaskir,
If I get another IP address from my ISP and statically address the laptop.  Will that work?

Commented:
Yes that will work, but you will need to ask your ISP to give you another IP, which wont be that easy if you are using PPPoE, but will work easily if its just plain ethernet after the modem.

Commented:
Basicly, if you are using PPPoE, you will get another set of username/password pair, and you will need to manually dial the PPPoE from your laptop, but without knowing exactly how you connect with the firewall/router thats already behind the modem, we can only guess :)

You can easily find out if you login to the firewall/router and look how its WAN interface is configured.

Author

Commented:
The switch that I am hooking up to is in front of the firewall...

Commented:
Yes, exactly. So you need to get the IP on your laptop the same way that the firewall gets its IP on the WAN interface. If its PPPoE or any other kind of tunneling, your laptop needs to do that as well.

Its its just plain ethernet, then its your ISP limiting the IPs behind your modem to 1, which is already taken by your firewall.

Author

Commented:
tomaskir,
Ok, I waited till after hours and then I tried hooking up my laptop straight to the cable from the modem and used the IP address assigned to us along with the ISP's default gateway and dns addresses and still nothing.  

Commented:
So you basicly disconnected the switch behind the modem and then connected your laptop straight into the modem and it didnt work.

That most probably means your are using PPPoE or another form of tunneling, as I mentioned before. Do you have admin access to the current firewall? That will be the easiest, fastest and most sure way to know how you are connecting to your ISP.

Author

Commented:
I looked at the firewall and its configured at "Static" for the WAN interface

Commented:
Alright, that means no tunneling is being used and its straight ethernet.

Unless there is scecific MAC bindings on the modem itself, when you disconnect the firewall and connect the laptop in its place and configure same IP, gateway and DNS, you should be able to reach internet straight from your laptop.

Please make sure you dont have the laptop and firewall connected to the switch behind the modem at the same time, otherwise you will have MAC - IP binding conflict and it will not work.

Author

Commented:
I connected the ethernet cable straight from the modem to the laptop.  Our ISP uses the same modem for our phone and internet now.  They say it can do both.  Could that be a problem???

Commented:
Since its working currently with the current firewall, the problem is that some configuration on your laptop is causing it not to work.

What happends when you connect to the modem, configure the proper IP, gateway and ping 8.8.8.8?

Can you ping the gateway. What does traceroute to 8.8.8.8 say? (tracert 8.8.8.8 on windows)

Author

Commented:
Tried all and everything "Timed Out"  I can't ping google.com or yahoo.com either.  

It's been a long day... can we pick this up again tomorrow morning about 9am?

Commented:
I will be doing some off-site work tommorow, so I will be back on EE in about 18-20 hours, but other people on here should be able to help you out easily :)

I will check this when I get back to my PC.

Commented:
Had an idea, try to set your laptops MAC to the same MAC your firewall uses on WAN
Commented:
Finally had time to get back to this issue and finally called the ISP and they had to come fix it at thier modem.  Not sure what they exactly did...they don't like to share sometimes.  Thanks for the help!

Author

Commented:
I had to call ISP and they fixed it at thier modem.  Nothing else worked.

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