BGP MED preference (0 vs NULL)

[tomek0001]

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

[Peter Paluch · Accepted solution]

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

[tomek0001]

Thank you Peter.

As a reference to other here is another link that talks about the MED not being set.

http://books.google.com/books?id=-IcqbmFG4_UC&pg=PA101&lpg=PA101&dq=cisco+default+med&source=bl&ots=NfE6A_Kakm&sig=BZbdqxICobFMtVoNLSGg0LSUUHE&hl=en&ei=2ch5S4vqBY21tgfVldG3Cg&sa=X&oi=book_result&ct=result&resnum=7&ved=0CCYQ6AEwBg#v=onepage&q=cisco%20...

Thanks

Tom

[Peter Paluch]

Tom,

Thank you for the link!

Best regards,

Peter