If ISP3 and ISP4 get the networks from your AS through the Internet with a short AS_PATH, there's nothing you can do... Ok, you can always shorten your prepends, but this doesn't guarantee they will prefer a certain path to your AS.
Considering that ISP3/4 got your AS with the prepends and without it is quite correct. That is because they got one path you you AS for your ISP1 (without the prepend) and the other path from ISP2 with prepend. Now the BGP best path selection is steping in. They may have multiple paths to your AS but only one is best (as you probably already know). Now while your ISP 1 is up and runing you get your traffic from that side and I bet that in the BGP tables of ISP3/4 they have your network as best path through ISP1. Let say ISP1 goes down. After about 180 seconds (default value) the entry in ISP3/4 tables about you network that was pointing the best path through ISP1 will dissapear and the best path will be through ISP2. And that is what you wanted to achieve right :-))
We are pleased to announce availability of Beta software for 16.6.3.
16.6.3 will be the second rebuild on the 16.6 release train targeted
towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are
looking for early feedback from customers befor...
Introduction Featured Speakers Luis Espejel is the Telecommunications
Manager of IENova, an Oil & Gas company. Currently he works with Cisco
IOS® and Cisco IOS XE platforms, and NX to some extent. He has also
worked as a Senior Engineer with the Routing P...
In this session you can learn more about Layer 3 multicast and the best
practices to identify possible threats and take security measures. It
provides an overview of basic multicast, the best security practices for
use of this technology, and recommendati...