How to detect high bandwidth causing slow Internet connection

Posted on 2007-08-04
Last Modified: 2013-11-05
All of sudden, Internet connection is really slow. File transferring or application access within LAN is no issue. Having 20 users, there is OK for no Internet connection temporarily. The network structure is simple, Internet > Cisco 837 ADSL router > Cisco PIX 501 firewall > 3COM 24 ports normal switch > 20 hosts.

With only one host direct connect to PIX 501 firewall, the Internet connection is fast, PING result shown avg 20ms.

With only one host direct connect to 3COM switch alone and unplug all other RJ45 cable, the result is same as above.

With all hosts connected to the 3COM switch, the Internet connection is really slow, and ping result shown above 1000ms.

After works, all employees gone home, the Internet connection is fast, ping result shown avg 20ms.

I am not quite sure which host is utilising high bandwidth causing the Internet connections is damn slow.

Please help
Question by:chekfu
    LVL 87

    Accepted Solution

    Check the workstations for malware and p2p software that might be downloading software. Use adaware, Spybot S&D, and hijackthis for that. You can also use wireshark to analyze the LAN, that should give you an idea of which PC's use most bandwidth.

    You can paste the log of the hijackthis of the suspected PC here.
    LVL 79

    Assisted Solution

    NTOP may give you better indicators of where all the traffic is coming from
    LVL 1

    Expert Comment

    Forced accept.

    EE Admin

    Featured Post

    Top 6 Sources for Identifying Threat Actor TTPs

    Understanding your enemy is essential. These six sources will help you identify the most popular threat actor tactics, techniques, and procedures (TTPs).

    Join & Write a Comment

    This article will cover setting up redundant ISPs for outbound connectivity on an ASA 5510 (although the same should work on the 5520s and up as well).  It’s important to note that this covers outbound connectivity only.  The ASA does not have built…
    Managing 24/7 IT Operations is a hands-on job and indeed a difficult one. Over the years I have found some simple tips and techniques to increase the efficiency of the overall operations. The core concept has always been on continuous improvement; a…
    Here's a very brief overview of the methods PRTG Network Monitor ( offers for monitoring bandwidth, to help you decide which methods you´d like to investigate in more detail.  The methods are covered in more detail in o…
    In this tutorial you'll learn about bandwidth monitoring with flows and packet sniffing with our network monitoring solution PRTG Network Monitor ( If you're interested in additional methods for monitoring bandwidt…

    730 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    18 Experts available now in Live!

    Get 1:1 Help Now