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456 Views 4 Replies Latest reply: May 4, 2012 7:54 AM by JZ RSS

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BGP MED Calculation

May 4, 2012 5:05 AM

Flexin 120 posts since
Feb 2, 2010

Hi guys.


have a quick querey about BGP med. I thought that med was always set to 0 unless changed by a route map . I have been running a ospf topology with 2 seperate bgp edge routers connecting to one singular bgp speaker router and the med is being set automatically.


How is this value set and what makes up the calculation.


i have done some testing and i have found bandwidth of a link in the path affects it but would like to know how its making this descision.


thanks guys



  • Currently Being Moderated
    1. May 4, 2012 6:09 AM (in response to Flexin)
    Re: BGP MED Calculation



    If you originate the prefix via redistribution or with the network command, the IGP meric will be copied to the BGP MED value when advertising to eBGP peers.  If you originate the prefix with the aggregate-address command, the MED value is not copied.  That's my understanding.

  • Currently Being Moderated
    3. May 4, 2012 7:42 AM (in response to Flexin)
    Re: BGP MED Calculation

    Not sure.  I'd have to lab that up and I'm not in a position right now to do that.  Maybe someone jump in and lab that up real quick.

  • JZ 34 posts since
    Jul 28, 2009
    Currently Being Moderated
    4. May 4, 2012 7:54 AM (in response to Erick)
    Re: BGP MED Calculation

    I just labbed this. And sure enought. When doing an aggregate the MED isn't copied to the aggregate. You can however use an attribute-map with the aggregate command to set a metric.





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