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Internet connection Intermittent

Hi everybody,

I'm facing an issue with a customer where the internet connection is intermittent. The topology is as follows:

Network Topology.png

This deployment was needed because the Cisco router has only one FastEthernet Interface and a Serial Interface. The serial is use for a dedicated channel and the FastEthernet for the LAN connection. The Cisco router is the Default Gateway to the LAN and it has a default route that forward all the unknown traffic towards the AT&T modem to reach internet. (route

Sometimes the internet connection gets down and some other it only has high response times. AT&T has changed the DSL Modem but the problem persists. I starting to think the proble could be the connection between the Cisco Switch and the Router. I checked the interfaces and put the Output in the Cisco Output interpreter and it point to some Underruns and Overruns. Also I checked the buffers and the Output Interpreter said that it could be a Buffer Leak. I'm not really into the Buffer stuff so I don't know what to do to troubleshoot this.

I'm attaching you the sho-tech for both the Router and the Switch just in case you can give me a light to solve this issue.

Thanks in advance


Hall of Fame Super Bronze

Re: Internet connection Intermittent

Your switch and router output looks fine. I'm willing to bet DSL is the issue here. If you want to eliminate the router from the equation, setup a test PC with gateway pointing to the DSL modem. When the issue occurs, go to the test PC and see if the internet is down or  having high response. If it is, the router is out of the equation and the problem is with the DSL connection.