BGP Cost Community and Point of Insertion

[walter1972]

Hi

Looking at the BGP Cost Community, I keep reading about how this influences the BGP best path selection process at the point of insertion (POI). Does this mean that the decision is taken immediately after step 8 in the Best Path Algorithm - ie Prefer the path with the lowest IGP metric to the BGP next hop?

For some reason I cannot get my head round this POI stuff.

Thanks

[Harold Ritter]

Walter,

The POI indicates when, in the BGP best path selection process, the cost community is taken in consideration. There is only two choices for the value of the POI:

Router(config-route-map)#set extcommunity cost ?

<0-255> Community ID

igp Compare following IGP cost comparison

pre-bestpath Compare before all other steps in bestpath calculation

Router(config-route-map)#set extcommunity cost

So as you can see it can be either compared before everything else (pre-bestpath) or right after the IGP cost comparison (igp).

Regards