Denying DHCP Request From Unauthorized Sources

Posted on 2009-04-26
Last Modified: 2012-05-06
I was wondering what how i could prevent unauthorized clients from broadcasting dhcp in my network. I have 2 authorized dhcp servers which i need to allow but i need to stop clients from pluggin their network connection into a lan port and broadcasting dhcp.  I have a cisco 2811 router
Question by:v46n
    LVL 1

    Accepted Solution


    It is a bit difficult to block these rogue DHCP servers, but if you also have a Cisco switch connected to the router, you may be able to use what's called "DHCP snooping."

    Here are some references:

    LVL 2

    Author Comment

    yea we have a cisco switch behind every router. i will look a the examples. thank you

    Write Comment

    Please enter a first name

    Please enter a last name

    We will never share this with anyone.

    Featured Post

    How your wiki can always stay up-to-date

    Quip doubles as a “living” wiki and a project management tool that evolves with your organization. As you finish projects in Quip, the work remains, easily accessible to all team members, new and old.
    - Increase transparency
    - Onboard new hires faster
    - Access from mobile/offline

    Suggested Solutions

    Tired of waiting for your show or movie to load?  Are buffering issues a constant problem with your internet connection?  Check this article out to see if these simple adjustments are the solution for you.
    In the world of WAN, QoS is a pretty important topic for most, if not all, networks. Some WAN technologies have QoS mechanisms built in, but others, such as some L2 WAN's, don't have QoS control in the provider cloud.
    After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
    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…

    760 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

    11 Experts available now in Live!

    Get 1:1 Help Now