Quick Scenario -2 – Bgp Communities – (no-advertise)

No Comments

Hi,

2nd post in the quick series is about BGP community no-advertise

Community – No-Advertise

“No-Advertise is similar to No-export, While no-export does not export routes to another AS, this goes further and it will not export route to both ebgp or ibgp neighbors as well.”

Requirement – Make sure R1 advertises its routes to R2, and R2 should not advertise the routes to either EBGP or IBGP neighbors

Topology

TOPOLOGY

Before confiuring anything

before-community

 

ON R1

 

access-list 99 permit host 1.1.1.1

route-map NO-ADV-COMM permit 10
match ip address 99
set community no-advertise

router bgp 100
nei 9.9.12.2 route-map NO-ADV-COMM out

final

 

Regards

Rakesh

 

 

 

 

 

Quick Scenario -1 – Bgp Communities – (no-export)

No Comments

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

Close Bitnami banner
Bitnami