Route Reflection Topology Models
National networks are usually laid out in concentration points across geographical regions. Providers have points of presence (POPs), sometimes called hubs, in different regions in the U.S. with high-speed links connecting different locations in a partial-mesh topology. The route reflector concept can be used to logically interconnect the routers running BGP in a pattern that follows the physical topology. Figure 9-5 illustrates a complex arrangement featuring route reflector..
Although hosting has been around almost as long as dedicated access services, it has become very popular over the past few years, with many service providers specializing in this market. Large providers that focus on dedicated hosting are commonly referred to as content providers. These providers usually develop highly fault-tolerant data center facilities that house cabinets or racks in which both enterprise and Web hosting customers can lease space and collocate servers and..
So far in this chapter, most of the discussion has been about examining existing addresses and subnets. Before deploying new networks, or new parts of a network, you must give some thought to the ranges of IP addresses to be allocated. Also, when assigning subnets for different locations, you should assign the subnets with thought for how routes could then be summarized. This section covers some of the key concepts related to subnet allocation and summarization. (This s..
NTP is used for accurate time-keeping and can, for example, reference atomic clocks that are present on the Internet. NTP is capable of synchronizing clocks within milliseconds and is a useful protocol when reporting error logs (for instance, from Cisco routers). NTP is useful for security/incident event correlation across multiple security devices and helps to determine the exact time of the event. For NTP, the defined ports are UDP port 123 and TCP port 123. NTP can ..
Summarizing Outbound Routing Information
By default, BGP will try to summarize routes. This is not always desirable, though, which is why we have explicitly disabled this feature in many of the examples in this chapter. In fact, many engineers prefer to manually summarize their routing tables because they want to control what gets summarized and what doesn't. The first problem with auto-summarization is that it is strictly classful. Your AS may not control all of the subnets in a classful network, and even if you d..
