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Community Member

BGP MED preference (0 vs NULL)

Hi

Does anyone know what's cisco's preference when dealing with a path that has a MED set to 0 and a path that does not have a MED set (assuming everything else is default)?

Thank you,

Tom

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Cisco Employee

Re: BGP MED preference (0 vs NULL)

Tomek,

As far as I know, this depends on the setting of the BGP process.

By default, if the MED attribute is missing, the IOS assigns the value of 0 to the route. You can change this behavior using the command bgp bestpath med missing-as-worst in which case the missing MED attribute will be internally assigned the value of 4294967294.

You may want to read the following link to the command reference:

http://www.cisco.com/en/US/partner/docs/ios/iproute/command/reference/irp_bgp1.html#wp1012195

Also, this document may be very interesting to read:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml

Best regards,

Peter

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Cisco Employee

Re: BGP MED preference (0 vs NULL)

Tomek,

As far as I know, this depends on the setting of the BGP process.

By default, if the MED attribute is missing, the IOS assigns the value of 0 to the route. You can change this behavior using the command bgp bestpath med missing-as-worst in which case the missing MED attribute will be internally assigned the value of 4294967294.

You may want to read the following link to the command reference:

http://www.cisco.com/en/US/partner/docs/ios/iproute/command/reference/irp_bgp1.html#wp1012195

Also, this document may be very interesting to read:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml

Best regards,

Peter

Community Member

Re: BGP MED preference (0 vs NULL)

Cisco Employee

Re: BGP MED preference (0 vs NULL)

Tom,

Thank you for the link!

Best regards,

Peter

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