Routers can easily determine the shortest AS_PATH length by using a few rules that define how to account for all four parts of the AS_PATH—the AS_SEQ, AS_SET, AS_CONFED_SEQ, and AS_CONFED_SET. Additionally, routing policies can change the number of ASNs in the AS_PATH. Table 13-12 summarizes the key points regarding AS_PATH length. Table 13-12 Features that Impact the Total Number of ASs in the AS_PATH Length Calculation The typical logic at this step simply requi..
Using the ip default-network Command
RIP and EIGRP can inject default routes by using the ip default-network command. To do so, the following must be true on the local router: ■ The local router must configure the ip default-network net-number command, with net number being a classful network number. ■ The classful network must be in the local router’s IP routing table, via any means. ■ For EIGRP only, the classful network must be advertised by the local router into EIGRP, again through any means. ..
The original motivation for developing EIGRP was simply to make IGRP classless. But early in the development the engineers working on the project recalled some academic proposals for a new kind of convergence algorithm and decided to use that algorithm in their extension of IGRP. The result was a protocol that, while retaining some concepts introduced with IGRP such as multiple metrics, protocol domains, and unequal-cost load balancing, is distinctly different from IGRP. EIG..
As a designer of secure networks, one of the first things you must consider is the vast interdependency of today's larger networks. The Internet is the best example, but within each organization there exists a microcosm of the Internet. From an attacker's perspective, these interdependencies allow for the attacker's goals to be met in any number of ways. As an example, assume an attacker wants to bring down your website. The following list outlines the attacker's options: ..
Network Security Promotes Good Network Design
Although it happens far less often now, I still occasionally sit down with a customer who says, "OK, the network design is done, now we need to think about security. We're certain we need a firewall and have also heard something about IDS." Designing secure networks in this manner puts you on a fast track to a network design in which the security is tacked on, interferes with the performance of the network, and is viewed by the rest of the Information Technology (IT) staff a..
