One Comment on “Drag the BGP attributes on the left to the boxes on the right in the correct order”

1. jslaven says:

   April 14, 2015 at 11:27 pm

   1. Next-hop accessible – Drop the update, next hop must be reachable in local routing table

   2. Largest Weight – Locally significant to router (to manipulate outbound traffic)

   3. Largest Local Preference – Propagated throughout the AS (to manipulate outbound traffic)

   4. Locally originated BGP path – Prefer path originated by BGP running on this router; network, redistribution, aggregate-address commands; network/redistribution chosen over aggregate-address

   5. Shortest AS path – bgp bestpath as-path ignore negates this attribute in the route selection; AS_SET counted once; AS_CONFED_SEQUENCE not counted in AS_PATH length (to manipulate inbound traffic)

   6. Origin – IGP < EGP < Incomplete

   7. Lowest MED – By default, compared for routes from the same neighboring AS; not compared for routes received from different ASs unless bgp always-compare-med; bgp deterministic-med can be used (to manipulate inbound traffic)

   8. eBGP < iBGP – Prefer external path to internal path

   9. Lowest IGP metric – Prefer path through the closest IGP neighbor (with lowest IGP metric to the BGP NEXT_HOP IP address)

   10. BGP Multipath – By default, BGP installs only a single route into the routing table

   11. Oldest Path – When both paths are external, prefer the path that was received first (oldest); omit this step when bgp
   best-path compare-router id is used

   12. Lowest router ID – Router ID is the highest IP address on the router (preference for loopback addresses); use bgp router-id to set router ID; if path contains RR attributes, ORIGINATOR_ID is substituted for the RID

   13. Minimum Cluster_List – If the ORIGINATOR_ID/router ID are the same for multiple paths, prefer path with minimum cluster_list length

   14. Lowest neighbor address – Address corresponds to the remote peer that is used in the TCP connection with the local router

   Hop with me to my next story since I know about it.

   The largest weight I've ever been was when I worked with the largest locally preferred group of engineers I've ever known. They originated from the local BGP tribe and only used the shortest AS path to arrive at their origin using IGP-EGP-Incomplete highway.

   As for me, I originated in the MED and my external BGP family was lower in rank than my internal BGP family. When we traveled our relatives we were lucky in that we were allowed to pay lowest IGP metric to use multiple BGP paths to get to my grandmother's house. It got to be boring because we would always take the oldest path and arrive at the lowest router ID where my grandmother lived. A few of her relatives lived together in the smallest cluster-list I've ever seen. Amazingly my grandmother had the lowest address of all her neighbors.

   
   
   
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