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..
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..
Pure Point-to-Point NBMA Networks
The pure point-to-point network is the simplest of all the setups, and it allows maximum control over the network. Each point -to-point subinterface can be configured to maintain a separate bandwidth, if each VC has a separate capacity. Again, recall the three basic rules: Enhanced IGRP traffic should not exceed the capacity of the virtual circuit. Total Enhanced IGRP traffic for all the virtual circuits cannot exceed the actual line speed. Bandwidth configured for Enha..
You have seen earlier that to make forwarding decisions, edge LSRs consult not only LFIB but also FIB tables. Although the label-based forwarding procedure is simple and conducive for high-performance forwarding, nevertheless edge LSRs still must perform conventional IP address lookups during label-imposition and sometimes during label-disposition operations. If you consider an LSR that is to act as a transit LSR for all traffic, in theory the LSR should be able to forward al..
The Cisco Kron facility is similar to the Unix Cron facility in that it allows you to schedule commands to be executed at regular intervals. In essence, it allows you to automate certain administrative functions that the router administrator would otherwise have to perform manually. Of course the major advantage is that once configured correctly, the Kron facility issues the commands at the exact time required and without the chance of typos. In addition, it does not require ..
