I don't think I ever said that ISP-B would announce the /19. That would only be announced by ISP-A. ISP-B would only announce the /24 that has been delegated to it. If the ISP-A/ISP-B link goes down then the /24 would be seen only via ISP-C which is the desired result. On 10/10/2016 9:16 AM, joel jaeggli wrote:
On 10/10/16 9:04 AM, Roy wrote:
The solution proposed allows ISP-B to use both paths at the same time, needs ISP-C to minimal changes, and has low impact on the global routing tables.. I have successfully used it in the past and my old company is still using it today.
Having two parties in control of a prefix announcement is a bit of a disaster. ISP A becomes partitioned from isp B isp B does not withdraw the covering aggregate and black-holes the of ISP A that lands on it's edge. bummer.