Will BGP router learn route advertised by IBGP router

[Cisconew]

Hi All,

I have configured BGP on R1,R2 & R3.

R1 & R2 : IBGP : (ASN: 65100)

R3 - ASN: 64519

R2 advertised 192.169.1.0/24 network. 

R1 & R3 received that route. 

If i shutdown the direct link from R1 to R2(Interface (G 0/1), R1 is not able to learn route 192.168.1.0/24 through R3.

Can someone explain, why ?

Routes learned:(When interface is UP)

 Route not learned(when interface is shutdown)

[Georg Pauwen]

Hello,

what is 192.168.1.0, an (loopback) interface, a static (null) route ?

[Cisconew]

It's a

loopback interface ip address>

[Harold Ritter · Accepted solution]

Hi @Cisconew ,

The route is rejected by R1, because its own AS number (65100) is contained in the update AS PATH. The AS PATH loop prevention mechanism will not allow that.

Regards, 

[Cisconew]

Thank you:  I understand AS_Path loop prevention Mechanism.

[Translator]

AS PATH loop defense mechanism