Building Scalable Cisco Internetworks (BSCI) Exams
As I write this exam dissection, the underlying BSCI exam is about to change: the current exam is #640-901, and a new version, #642-801, was in beta test until June 2003. Candidates can sign up for the older exam until Sept. 7, 2003 and can take it until late October 2003, which means that only those readers who peruse these pages shortly after they’re published will even be eligible to take the older of these exams. That’s why I concentrate on the new exam (with pointers to several excellent analyses of the older exam for those who may need such information in Table 2).
As an exam that pertains to the CCNP, CCDP and CCIP certifications, BSCI is an important feature on the Cisco Professional certification landscape. Earlier versions of this exam are rated by many as among the hardest of exams. Otherwise, its basic characteristics are much like those for other Cisco certifications, as shown in Table 1. Like its predecessor, this exam includes several simulation-based questions. Given that advanced routing topics are a primary focus, it’s also not unreasonable to assume that routing topics will be the focus for hands-on exam interactions. (Earlier analyses have emphasized candidates’ needs for strong working familiarity with configuring or managing IS-IS, BGP, OSPF, variable length subnet masking (VSLM) and route summarization.)
BSCI Exam Topics and Focus
Without going into too much detail, and without explaining all the protocols and routing behaviors you’ll be tested on, here’s an expanded list of topics and coverage adapted from the list of official exam topics:
- Understand all key information elements routers need to know to route data, particularly how available route information is represented, stored and shared.
- Understand basic operations of and distinctions between classful and classless routing protocols, where the former use fixed notions of prefix length as context for routing updates, such as RIPv1 and IGRP, and the latter include explicit prefix length with router updates, such as OSPF, EIGRP, RIPv2, IS-IS and BGP. Note also that route summarization techniques like VLSM or CIDR work only with classless routing protocols.
- Be able to compare distance vector and link state routing protocols, particularly as the notion of distance is represented (by default and by explicit configuration) in RIP, IGRP, EIGRP, OSPF and BGP.
- Understand how IP addresses may be extended and how variable length subnet masks (VLSMs) may be used for this purpose. Working knowledge of VLSM and other address extension techniques like NAT and private IP addresses is required.
- Be familiar with features and operation of EIGRP. In particular, this means understanding key EIGRP commands, functions of IP multicast for updates, route summarization techniques and how EIGRP works as a hybrid routing protocol.
- Be familiar with features and operation of single-area and multi-area OSPF. This means understanding the Hello protocol, including Router ID, intervals, neighbors, Area ID, router priority, DR and DBR IP addresses and so on. Likewise, this means working with interface commands for single-area OSPF and with the various types of routers and link-state advertisements (LSAs) that are likely to occur in multi-area OSPF environments.
- Understand fully basic OSI networking terminology, how network layers function in the OSI reference model and how OSI protocols map to that model. Candidates must know and understand how OSI network layer protocols work and behave, formats of NSAP addresses, link cost calculations and how IS-IS routing domains are configured and operated.
- Be able to compare and contrast how integrated IS-IS and OSPF protocols work, behave and scale.
- Understand the various types of IS-IS routers and the roles they play in design of IS-IS areas
- Be familiar with the hierarchical structure of IS-IS areas, and with Level 1 (L1) and Level 2 (L2) routing behavior and routing tables and how such tables are built.
- Understand what’s involved in establishing adjacencies in BGP.
- Be familiar with features and operation of BGP, including distinctions between internal and external BGP, the role of static routes and how autonomous system numbering works. It’s also important to understand both well-known and option BGP attribute types and how to use them to configure and manage BGP.
- Understand how BGP policy-based routine functions within an autonomous system.
- Explain how to use redistribution between BGP and various Interior Gateway Protocols. In essence, this means making all routing protocols mentioned so far work together, so redistributing routing updates across routing protocols is crucial. Likewise, issues related to migrating from IGRP to EIGRP, integrating RIP and OSPF routing domains and configuring Cisco and non-Cisco routers to share a common routing protocol are all important topics to investigate.
BSCI Implementation, Configuration, Design and Troubleshooting Requirements
If the preceding exam information can be characterized as what candidates must know—that is, the various concepts, models, protocols, design and deployment issues covered in the exam—Cisco’s description of the BSCI exam also states what candidates must be able to do to pass the exam—that is, the kinds of configuration and implementation scenarios they should be able to handle and the kinds of designs and troubleshooting situations they can deal with. Where proper operation of a routing environment must be verified, the complete definition of such operation is based on whatever guidelines or parameters are defined in stated requirements, along with other related information supplied as part of the exam questions or problems.
This part of the exam description addresses typical implementation and configuration assignments candidates should be able to handle:
- Based on a set of network requirements, addressing schemes and other setup parameters where needed, candidates must identify the steps involved in configuring some particular routing environment. They must also verify proper operation of all affected routers. Each scenario or simulation is likely to involve any one of the following routing environments: EIGRP, single-area OSPF, multiple-area OSPF, integrated IS-IS or BGP. Multiple scenarios or simulations can occur on a single exam, so strong familiarity with all named types of environments is essential.
- Candidates must identify the steps necessary to select and configure various methods to control routing update traffic. This includes a thorough understanding of the roles that routing maps play in managing update traffic and behavior.
- Candidates must identify the steps necessary to configure router redistribution within a network. These include a thorough working knowledge of the Cisco Seed Metric and modification of administrative distance values for routing costs, as well as the redistribute command.
- Candidates must identify the steps necessary to configure policy-based routing on a network using route maps. Here, it’s important to understand how route maps differ from access lists and the specific behaviors of set and match commands often used to configure and manage such maps.
In the area of network and routing design, candidates should be ready to encounter and address the following situations and requirements:
- Understand and be able to describe the three-layer hierarchical design model for networks, and explain the function of each layer—namely, Access, Distribution and Core. Working knowledge of Cisco best design practices helps a lot here.
- Within a set of specific requirements, choose the network protocol that best satisfies such requirements, and be prepared to explain and justify that choice.
- Given a set of specific requirements, identify the correct IP addressing sche