Limitation of Route Reflectors in IBGP Mesh Design

C.

When designing an iBGP mesh, it is important to consider the scaling limitations of full mesh iBGP, where each router in the topology has a full iBGP session with every other router in the topology. As the number of routers in the topology grows, the number of iBGP sessions grows exponentially, making the management of these sessions and the overhead associated with the processing of updates challenging.

One approach to address the scalability challenges of full mesh iBGP is to use route reflectors. A route reflector is a router that is designated to reflect iBGP updates to other routers in the topology, rather than forwarding them to all other routers as in a full mesh iBGP topology. In a route reflector topology, routers are divided into two types: route reflectors and non-route reflectors. The non-route reflectors establish a full iBGP mesh with the route reflectors, and the route reflectors reflect iBGP updates to other routers in the topology, reducing the number of iBGP sessions needed.

While using route reflectors can address the scalability challenges of full mesh iBGP, there are some limitations to consider. Let's review each answer option:

A. The configuration complexity on the routers will be increased. This is not a valid limitation of using route reflectors. In fact, using route reflectors can simplify the configuration of iBGP on the routers, as they only need to establish full iBGP sessions with the route reflectors, rather than with all other routers in the topology.

B. Route reflectors will limit the total number of routes in the topology. This is also not a valid limitation of using route reflectors. Route reflectors do not impose any limit on the number of routes that can be supported in the iBGP mesh.

C. Multipath information is difficult to propagate in a route reflector topology. This is a valid limitation of using route reflectors. In a route reflector topology, multipath information may be lost as the route reflector only selects and propagates a single best path to other routers in the topology. This can lead to suboptimal routing decisions and reduce the network's ability to fully utilize available paths.

D. Route reflectors will cause an opportunity to create routing loops. This is also not a valid limitation of using route reflectors. Route reflectors are designed to prevent routing loops by using the "cluster ID" attribute to identify updates that have already been reflected and prevent them from being reflected again.

In summary, when considering the use of route reflectors in an iBGP mesh design, it is important to be aware of the limitation related to multipath information propagation. However, overall, route reflectors are a useful tool for addressing the scalability challenges of iBGP mesh design.