Hey Guys, Just a couple of notes:
- You can certainly set prepends without communities. Setting prepends, just like MED, is a function of the outbound route-map on the BGP peer. You can *match* based on the community if you want to, but you can also match of an acl etc. - MED is generally only used when talking to the same AS. - By default a missing MED on a Cisco is treated as 0 (which would then become the most prefered path - Lower MED is prefered). You can change this by using the "bgp bestpath med missing-as-worst" configuration option which treats a missing MED as infinity. - By default MED is only compared between routes from the same AS. If you want to use MED for tie-breaker path selection between different AS's, you would use "bgp always-compare-med". This way if I learn about AS10 from both AS20 and AS30, I can use the MED (as set by my peers, not AS10) to select between otherwise equal preference routes. - For a useful explanation of the differences between "bgp always-compare-med" and "bgp deterministic-med", refer to http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094925.shtml . Those are just some quick points on this discussion. I am happy to be corrected if I have the above wrong. Regards Kurt (@networkjanitor)
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