DSL Troubleshooting

Trouble Shooting DSL, Cable, & Dial-up connection & Routing issues

Here are a few simple tools and techniques that we can use to understand where a problem may be with ISP connection & Routing issues "Page cannot be displayed" etc...

• First we need to determine if the computer is even connected to the ISP's Radius server and receiving an IP address.

Using the winipcfg /all command in the RUN box, or in the command prompt does this.



For Dial-up this is simple, there will be only one adapter listed (Dial-up Adapter) or (AOL Dial-up Adapter)

If IP address is 169.254.X.X the computer is not receiving an IP from the server (This is a WIN default IP)

If IP address is 0.0.0.0 they are not connected to ISP

If IP address is anything other than these configurations then they are connected and we can proceed to testing.

NOTE: DSL and cable will have several adapters (2 Ethernet for Cable) (one PPP adapter and one Ethernet Adapter for DSL). We must check all of them for the IP address.

• TESTING

Now that we have determined the computer is connected we can test the DNS & TCP/IP

Functions to see if the computer can compile TCP/IP packets and route them to a particular computer.

Using the PING command in the command prompt does this.

Type PING (space) http://www.(domain/ Name). COM

This will produce several results.

IP address

4 replies w/ the TTL info or Request timed out

How many packets were sent, received, and lost.



If the results produce “Destination host unreachable” or “request timed out” and (4) packets sent (0) received 100% loss. Then there may be a DNS (Domain Naming Service or TCP/IP issue w/ the computer)



We can then try to PING Yahoo by IP address (You may have to PING yahoo from your computer to get the IP address)

IF they can PING the IP address then insert the IP address in their browser to see if it will pull up the web page. If this works then R&R communications in add/remove programs then reboot and test.

If they cannot PING the IP address then R&R TCP/IP, Reseat NIC/modem or Re-install OS.

IF the computer can PING by Domain name & IP address but the browser cannot pull up web pages then R&R Browser.

(Try to use Yahoo they are a major port hole to the Internet and will allow us to PING their domain)

• TESTING NIC & throughput issues

We can test the NIC to see if it is functioning properly by:

Pinging the Loop back address 127.0.0.1

This will use TCP/IP to compile a packet and send it to the NIC causing it to reply back to the OS. If this fails then reseat the NIC into a different PCI slot and test again or replace NIC.



We can test the throughput by running a trace rout to the Domain that the computer is routing slow to. TRACERT http://www.(domain/ Name). COM will produce every hop that the TCP/IP packet makes from the NIC all the way to the Domain server.



If the computer times out on the first hop then the NIC needs to be reseated or replaced.

The second hop is the Gateway router (DSL or Cable Modem)

Every hop is a computer or router and the information of how long the packet took to pass through the router to its next destination. Any hop that times out or the TTL is much greater than the rest indicates a routing issue at that particular router and not in the computer. This helps us distinguish between a COMPAQ problem and an ISP problem.