That regexp (regular expression) is typically used to ensure that an AS that has connections to 2 separate Autonomous Systems (ISPs, typically) does not act as a transit AS and allow routes advertised by one ISP to be advertised over to the other.
So, AS 100 has a BGP connection to AS 200 and AS 300. As 300 advertises prefixes to AS 100, but AS 100 makes sure that it does not pass those routes, and instead advertises ONLY the local prefixes, as Jon pointed out.
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...