On Friday 28 September 2007 18:16, Mike Barnard wrote: > localprefs did the trick on my side... thats what > changed.
The recommended LOCAL_PREF configuration for local routes (i.e., routes to customers and routes to exchange points) should be higher than routes learned via upstreams. * directly connected customers should have the highest LOCAL_PREF value set, e.g., 150. * exchange point routes should have a LOCAL_PREF value lower than that used for directly connected customers, but higher than that used for transit routes, e.g., 120. * all other routes (routes learned via upstreams) could use the default LOCAL_PREF value, which is 100 in Cisco IOS and Juniper JunOS by default. You can have additional custom settings to add more control into your routing domain, but that's beyond the scope here :-). > for some reason, the Intelsat path was preferred over the > IX. the IX path had a metric of 1 and the Intelsat 0, of > course Intelsat would get all IX traffic heading to > one2net/spacenet/bushnet. Right, because in the BGP Route Selection Algorithm, the lowest MED (BGP metric value) wins. However, MED is the 6th step in the algorithm. If MED were used to decide the best next-hop, it might mean the AS_PATH you are receiving for the destination prefix is the same over your transit and local peering links. This would be *odd* as you "typically should" have a shorter AS_PATH for locally-learned routes, but not necessarily if the destination network is connected to the same upstream as you, i.e., Intelsat, in this case, and your peering link is connected to the border router your upstream is connected to as well. > what changed in the first place i don't know....but for > now, we've just thrown on some methylated spirit, a > bandage and some plaster... I would recommend standardizing on a high-enough LOCAL_PREF value for locally-learned routes, as well as connecting your exchange point peering link to a router closer to your edge (customers), separating it from your border/transit routers. Cheers, Mark.
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