In classic IBGP, the BGP boundary router needs to forward the route that is received from an EBGP peer to every other router within its own AS. This requires the use of a dedicated IBGP session for each router. Also, the BGP boundary router forwards routes that a router sources in the same way. The result is that a large number of IBGP sessions are required. BGP provides the route reflector feature to help to scale these sessions. Large BGP networks cannot properly scale without relying on performance-enhancing tools such as route reflectors. Route reflectors enable BGP routing information to be distributed in a way that does not require a physical full-mesh network. Implementation of such a network requires knowledge of the steps to properly migrate and configure route reflectors and the commands that are used to verify the operation of a configured network. This course introduces the steps that are required to successfully migrate an existing AS to BGP route reflectors. It also lists the Cisco IOS commands that are required to configure and monitor route reflectors.

As the number of routes in the Internet increases, demands on router CPU and memory resources on the router in a service provider will increase. BGP processing affects both router resources and network convergence time. Network convergence must be as fast as possible to ensure accurate routing information between domains. Router resources also must be optimized whenever possible. Cisco IOS performance improvements for BGP are designed to aid network administrators in achieving these goals. In this course, you will learn about various Cisco IOS performance improvements that have been designed to reduce BGP convergence time. This course includes discussions of convergence, BGP routing processes, and the effects of BGP routing processes on router CPU resources. The course also discusses the commands that are required to configure and monitor BGP for various Cisco IOS performance improvements. Improvements that are mentioned are PMTU discovery, input hold queue, BGP PIC, BFD, BGP NSF awareness, BGP scan time, advertisement interval, keepalive, and hold-down timers.

More than 600,000 prefixes are now on the Internet. Network administrators do not need or desire their routers to carry full Internet routing in many circumstances. Furthermore, protective controls are needed on customer-facing routers to ensure that a configuration error does not cause the accidental advertisement of prefixes from autonomous systems that did not originate them. BGP is designed for reliability and scalability. It has much flexibility regarding administrative policy controls, route selection, and performance tuning and scalability features. An advanced BGP configuration tool has been designed to improve BGP scalability and performance by reducing the number of prefixes that a router receives from a BGP neighbor. Scaling routers to meet the demands of full Internet routing and associated administrative policies requires protocols such as BGP with embedded scalability mechanisms. In environments where network administrators must configure many BGP peers, peer groups are a scalability tool that reduces both administrative overhead and router resource requirements. Typical service provider networks usually contain BGP-speaking routers that consist of many neighbors that are configured with the same administrative policies. These policies can be outbound route maps, distribute lists, filter lists, update source, and so on. You can group neighbors with the same update policies into peer groups to simplify configuration and, more importantly, to make BGP updates more efficient. In this course, you will learn about peer groups as a BGP scalability mechanism. Even when a BGP implementation is correctly configured and highly robust, the performance of the routing process on any given router is limited. Limiting the propagation of unstable routes, specifically when they are not beneficial to the network, becomes an important issue because it reduces the processing requirements of the router that is forced to process routing table state changes. Route dampening is a BGP feature that has been designed to reduce BGP processing requirements by minimizing the propagation of unstable routes to BGP peers. AS border routers, in any BGP implementation, cannot rely upon external peers to sufficiently shield the AS from routing table instability. Route dampening allows route instability to be contained at an AS border router that borders the instability. This course describes the purpose and operation of the route-dampening feature on Cisco IOS routers. This course also discusses the Cisco IOS commands that are required to enable route dampening, modify default dampening parameters, and release a route that has been suppressed because of dampening. Cisco IOS commands that are used to monitor route dampening are also discussed.