Hi,

This will be a series of posts in which i shall be posting some quick scenario labbings. Mostly i have designed these so that I can relate to some stuff which i do not often use, nevertheless will blog all small topics

Community – No-export

“NO-EXPORT is commonly used within an AS to instruct routers not to export a prefix to eBGP neighbors. For instance, subnets of a larger block can be advertised to influence external AS best-path selection, and those not required for this traffic engineering purpose may be tagged NO-EXPORT to prevent them from being leaked to the Internet (and thus contributing to unnecessary global routing table growth). If a neighboring AS accepts this community, it can be used to selectively leak more specifics for traffic engineering but limit their propagation to just one AS.”

Requirement – R1 has its loopback advertised to R3 via BGP. Make sure the advertisement stays within the AS and should not go to another AS Router in this Case R3

no-export scenario

Before community addition – Routing Table of R3

pic1

AS we can see below route is not seen R3.

pic2.final

Regards

Rakesh M