This topic is to discuss the following lesson:
Hub router already store NBMA of Spoke 2 when it was establish tunnel interface, but why when Spoke 1 send request NBMA address of spoke 2 to hub then hub need to forward it to spoke 2? why don’t it reply back directly to spoke 1?
You are correct that the Hub router does know the NBMA of spoke 2, however, when an NBMA request is sent, it must always be answered by the owner of the specific address. In this example, Spoke 1 doesn’t have the 172.16.123.3 address in its NHRP cache. It sends out an NHRP resolution request. The resolution request is not sent to the Hub as its destination, but is sent to the hub as the the path to the destination , that is, via Tunnel 0.
The NHRP resolution must always be answered by the owner of the IP address in question. In this case, it must be answered by the device with the NBMA address of 188.8.131.52, which is Spoke 2. This is why the request is forwarded to Spoke 2 and Spoke 2 is expected to answer.
I hope this has been helpful!
I got this now, It mean Spoke 1 send use Hub as it path to send NHRP resolution request to spoke 2.
Thank you so much .
I shut down HUB after spoke already establish dynamic connection between them. and all spoke and HUB are running RIP to advertise their loopback. since i shut down the HUB and clear IP route on spoke i found that RIP is never recover. it lost all route to loopback of another spoke.