Your PC’s MAC address is 0010.1111.2222. Your PC gets its IPv6 address using stateless autoconfiguration. What is your PC’s EUI-64 format interface ID?

1. 0010.11FF.FE11.2222
2. 0210.1111.FFEE.2222
3. 0210.1100.0011.2222
4. 0210.11FF.FE11.2222
5. 0000.0010.1111.2222

The correct answer is 4.

The EIU-64 format interface ID is created from the MAC address by setting the 7th bit of the 1st octet (the “unique” bit) to 1 and inserting FFFE into the middle of the address. In this scenario, the resulting interface ID is 0210.11FF.FE11.2222.

References:
For more questions like these, try our CCNA Cert Check

Related Courses:
ICND1 — Interconnecting Cisco Network Devices 1
ICND2 — Interconnecting Cisco Network Devices 2
CCNAX — CCNA Boot Camp v1.1

Your router has the following interfaces configured:
Loopback 0: 10.2.2.2/24
Loopback 10: 10.1.1.1/24
FastEthernet 0/0: 172.16.1.1/24
FastEthernet 0/1: 172.16.2.2/24

You configure OSPF. What is the OSPF router ID?

1. 10.2.2.2
2. 10.1.1.1
3. 172.16.1.1
4. 172.16.2.2
5. There is not enough information to determine the router ID.

The correct answer is 1

If the router ID is not specified with the router-id command and if the router has loopback interfaces with IP addresses when OSPF is configured, the OSPF router ID is the highest such address. Otherwise the router ID is the highest IP address configured on an active interface.

References:
For more questions like these, try our CCNA Cert Check

Related Courses:
ICND1 — Interconnecting Cisco Network Devices 1
ICND2 — Interconnecting Cisco Network Devices 2
CCNAX — CCNA Boot Camp v1.1

Routing and Switching Certifications

CCNP

The Cisco Certified Network Professional (CCNP) certification confirms your familiarity with the daily job tasks of professional network engineers who work on complex security, voice, wireless and video network solutions. Emphasizing the skills required to plan, implement, verify and troubleshoot local and wide-area enterprise networks, the initials “CCNP” after your name are more valuable now than ever.

Prerequisite: At least one year of networking experience and a valid CCNA certification or any CCIE certification.

Required Cisco Exams: 
642–902 ROUTE
642–813 SWITCH
642–832 TSHOOT

CCIE

Cisco Certified Internetwork Expert (CCIE®) certifies the expert-level skills required of network engineers to plan, prepare, operate monitor, and troubleshoot complex, converged network infrastructure. Professionals who achieve CCIE have demonstrated their technical skills at the highest level.

Prerequisite: There are no formal prerequisites for CCIE certification but candidates are expected to have an in-depth understanding of the topics in the exam blueprints and strongly encouraged to have three to five years of job experience before attempting certification.

Required Cisco Exams: 
Step One: CCIE Routing and Switching Written Exam
You must pass the two-hour, written qualification exam which covers networking concepts and some equipment commands before you are eligible to schedule the lab exam. The written exam now includes new scenario-based questions.

Step Two: CCIE Routing and Switching Lab Exam
The eight-hour lab exam tests your ability to configure actual equipment and troubleshoot the network in a timed test situation. You must pass the lab within three years of passing the written to achieve certification. Your first lab attempt must be made within 18 months of the written exam. The lab now requires hands-on troubleshooting, in addition to configuration.

Storage Certifications

CCIE Storage Networking certification designates expert-level knowledge of intelligent storage solutions using multiple transport options over long distances. It certifies that you have the in-depth experience to manage, deploy, and interconnect multiple types of data storage devices and data servers that enterprise users rely on today.

Success on the CCIE Storage Networking written exam and the CCIE Storage Networking lab exam declares that you have expert knowledge implementing and troubleshooting storage area networks, including LANs, MANs, and WANs over Fibre Channel, iSCSI, FCIP, and FICON and that you can demonstrate in-depth understanding of Layer 2 and 3 network infrastructure.

Prerequisite: While there are no formal prerequisites for CCIE Storage Networking certification, you are expected to have an in-depth understanding of the topics in the exam blueprints and are strongly encouraged to have three to five years of job experience before attempting certification.

Required Cisco Exams: 
Step One: CCIE Storage Networking Written Exam
You must pass the two-hour written exam covering topics such as storage device protocols, troubleshooting tools, and storage networking design, applications, and advanced management before you are eligible to schedule the lab exam.

Step Two: CCIE Storage Networking Lab Exam
The CCIE Storage Networking lab exam is an eight-hour, hands-on exam which requires you to configure a series of storage area networks to given specifications. Knowledge of troubleshooting is an important skill, and you are expected to diagnose and solve issues as part of the lab exam. You must make an initial attempt of the CCIE Storage Networking lab exam within 18 months of passing the CCIE Storage Networking written exam.

Related Courses
Cisco Certifications

We now have the same discussion with Storage Area Network (SAN) administrators. People running data centers ask to trim the bottom line but still want ultimate design and infrastructure flexibility in an era where servers are not purchased for specific applications but rather to increase resources in the virtual cloud. Cisco has released a new product line called Nexus that makes data center managers and technical architects think twice about their equipment needs.

To quell any bandwidth issues, the Nexus switches offer 10GB connectivity to the hosts with some I/O modules capable of 40GB and even 100GB per port. This means a single physical optical cable could provide a server SAN/LAN and high-speed connectivity. This makes a lot of people happy, namely the server administrators and data center managers. The first group is happy because you address their needs and the second group because you reduce the costs to provision servers on the network.

Merging the SAN / LAN and infiniband capabilities into one wire and switch defines the Unified Fabric. However, network administrators are often left with the task of understanding how this Unified Fabric is going to work. SAN administrators have to worry about logical unit numbers (LUNs), initiators, targets, masking, and zoning, as well as the well-being of their storage arrays. Network administrators will be responsible for taking the native Fibre Channel traffic out of the SAN area of the data center, and transporting it to the hosts using Unified Fabric.

Cisco switches such as the Nexus 5000 series offer several options such as built-in FCOE/CE (Classical Ethernet) ports, as well as native Fibre Channel expansion modules to be able to communicate and/or convert an existing Fibre Channel infrastructure. In addition, there are newer models, such as the Cisco 5548UP and 5596UP switches that offer a “Unified Port” that can turn any port into a native FCOE/FC or FCOE/CE, giving you the ultimate flexibility. To top it off, storage vendors now sell FCOE storage processors (SPs) that can replace the need for Fibre Channel at the source and eliminate the need for conversion.

The Nexus switches were born of a fusion between Catalysts and MDS and can handle everything an MDS could do in the past. As a network administrator, it is possible to use Role-Based Access Control (RBAC) to give “storage” permissions to the SAN administrators, and they can continue using tools like Fabric Manager with the Nexus without impacting LAN configurations.

The challenges for the network administrators are numerous. Classical Ethernet is built on a “connect anywhere” and oversubscription model where losing an Ethernet frame is not a problem. On the Fibre Channel side, however, the approach is totally different. Frames that are put on the wire are actually SCSI commands, and the SCSI protocol is built on a presumption that SCSI commands do not fail, and therefore there are no retransmission mechanisms built into the Fibre Channel Protocol.

FCOE does not change that behavior. In fact, FCOE doesn’t change anything but the envelope of the FC frame to make it readable by an Ethernet switch. In Unified Fabric, the segment that connects, for example, a Nexus switch to a server is called a Unified Wire since it will carry both CE and FCOE traffic.

QOS is very important in Unified Fabric since the FC traffic has a “lossless” guarantee. There are several components at play here, but in summary:

1. The Nexus switches tag the FC traffic with the highest priority, and
2. Virtual Output Queues (VOQ) can be involved for a switch to be certain that a path can be guaranteed for traffic, especially storage traffic.

What network administrators also need to understand are the overall configurations necessary to accommodate this new unified method. In a Unified Fabric model, the network interface cards (NICs) connecting the servers to their switches are called Converged Network Adapters (CNAs), and they are able to send FCOE and CE frames on the same wire. The FCOE Initialization Protocol (FIP) discovers the switch port it is connected to, which the Network Admin will have configured as a trunk carrying a Data VLAN and a Storage VLAN (later connected to a VSAN), and FIP will discover that information to connect. After that, the fabric login (FLOGI) and port login (PLOGI) process can continue for storage network and whatever else needs to happen on the CE side will continue as well.

The Unified Fabric model also brings several Ethernet enhancements to deal with this amalgamation of traffic, including two crucial ones: Link Layer Discovery Protocol (LLDP) and Data Center Bridging Exchange (DCBX). In the Cisco world, when two switches want to discover each other, they usually can exchange information automatically using the Cisco Discovery Protocol (CDP). However, it is proprietary and cannot usually discovery other vendor switches. LLDP operates at layer 2 as well and is open-vendor, so you can now advertise certain capabilities related to the Unified Fabric with it. LLDP will use a tag, length, value (TLV) field to advertise that the switch or server that you are operating will be able to speak the DCBX protocol.

DCBX will allow both endpoints to negotiate certain features such as:

Priority Flow Control (PFC): the ability to prioritize certain types of traffic within classes using virtual lanes. In standard QOS, we can, for example, look at what is CE and what is FCOE. With PFC, we can look into FCOE and identify specific conversations within the protocol, thus giving the network admin more granular control. Additionally, we will now be able to stop a single virtual lane as opposed to an entire interface if a PAUSE frame is received.

• Enhanced Transmission Selection (ETS): tied closely with PFC but enables strict QOS policies on virtual lanes within an interface, giving us the ability to separate the 10GB interface into smaller chunks of bandwidth.
• Logical UP/DOWN: the ability to shut down a certain type of traffic without affecting the rest of the traffic traveling on a particular interface. For example, a network admin troubleshooting a Unified Port could issue a “Shutdown LAN” command to remove all the CE traffic to find out of the CE traffic is an issue.

These capabilities can be discovered automatically between Nexus Switches and generation II CNA adapters, reducing the amount of configuration required by the network administrators. They should be easy to adapt to a multi-vendor network since DCBX is an IEEE standard (although some vendors have been trying to throw their own proprietary information in it).

A Unified Fabric is not something that is out of reach, but it must be considered seriously by all the parties involved. Some data center managers get hung up on the fact that it will save them money and forget about the initial capital expenditure that needs to take place. SAN administrators may want to stonewall the project due to a lack of understanding of what this will actually accomplish, losing the bigger picture goal, which is to remove all the “SAN only” network gear, and network administrators need a strong understanding of Fibre Channel to understand how to verify end-to-end connectivity with the F, E, TE ports, as well as FLOGI and FCNS.

Related Courses
DCUFI — Implementing Cisco Data Center Unified Fabric v4.0 (formerly DCNX5+7)
DCUFD — Designing Cisco Data Center Unified Fabric v3.0

Excerpted from Global Knowledge: The Main Components of Unified Fabric by Alex Marcotte

Let’s start with the use of debugging. The debug command is supported on both the ASA security appliance and the Cisco IOS^® router. An important and noteworthy implementation difference between the two platforms is that logging must be enabled for debug output to be seen on the router, but not on the ASA. A sample debug output for an IPSec Internet Key Exhange (IKE) Phase I exchange:

Jan 19 21:37:58 [IKEv1]: IP = 200.200.20.2, Error processing payload: Payload ID: 1
Jan 19 21:37:58 [IKEv1 DEBUG]: IP = 200.200.20.2, IKE MM Responder FSM error history (struct &0xc8f8bcc8)  <state>, <event>:  MM_DONE, EV_ERROR–>MM_START, EV_RCV_MSG–>MM_START, EV_START_MM–>MM_START, EV_START_MM–>MM_START, EV_START_MM–>MM_START, EV_START_MM–>MM_START, EV_START_MM–>MM_START, EV_START_MM
Jan 19 21:37:58 [IKEv1]: IP = 200.200.20.2, Removing peer from peer table failed, no match!
Jan 19 21:37:58 [IKEv1]: IP = 200.200.20.2, Error: Unable to remove PeerTblEntry

Most observers would agree that such output is quite cryptic, and, in most cases, requires a fairly thorough knowledge of the protocol to make sense of the messages. I remember needing a few minutes after observing the cryptic message along the lines of  “…packet is malformed and failed sanity check” for me to correctly conclude that this was caused by mismatched VPN preshared keys!

By contrast, using syslog often provides a “big picture” view instead of getting “lost in the weeds”.  Below is a screenshot of a very valuable tool now bundled with the Adaptive Security Device Manager known as the Real Time Syslog Viewer:

Not only does the use of the different colored fonts on the white background present a more appealing and “easier on the eye” format, but the colors were chosen such that the “cooler” colors (blue, purple) represent more trivial messages while the “hotter” colors (yellow and red (not shown)) represent the more serious events. Also, the three tabs at the bottom should not be overlooked as these provide additional event explanations, recommendations, and details for the highlighted row.

In conclusion, I don’t wish to appear too negative toward the use of appropriate “debug” commands.  They are well-suited to understanding the operation of a protocol, especially when coupled with a network sniffer application. Secondly, as I told numerous students, verbose output (versus no output) is usually best — an indication of success. However, for quick problem identification, the often unambiguous output of a real time log viewer can’t be beat.

Challenges

Ottawa Regional’s campus spans eight buildings, which are interconnected with a private fiber network. A physician office is connected to the main campus through T-1 circuits.

The hospital wanted to upgrade its 100 Mbps campus network to 10GbE. It also wanted to enhance network reliability and availability to meet the rigorous demands of healthcare IT, while minimizing complexity and reducing operating expenses. It was time for a new approach and “the new network.”

Ottawa Regional’s new campus network had to meet several requirements. First and foremost, it needed a high-performance infrastructure to support voice over IP (VoIP) and new healthcare information management software. Higher WAN speeds were also essential to support its enterprise virtual private network (VPN), remote access, and a quality voice experience.

The hospital also wanted to improve network resiliency. Its Ethernet switches were daisychained on the fiber, which meant that if one switch failed, the entire network could go down. Plus, the incumbent switches didn’t support Power over Ethernet (PoE), which the hospital needed to support IP telephony. Furthermore, the campus WAN architecture had a single point of failure that could negatively impact the hospital’s enterprise VPN, firewall, and WAN services.

Solution

The hospital deployed Juniper Networks routing, switching, and security solutions to build its new network and also installed new single-mode fiber between campus buildings to support high-performance networking. The campus network consists of Juniper Networks® EX Series Ethernet Switches. The EX4200 line of Ethernet switches with Virtual Chassis technology provides carrier-class performance in a single rack unit form factor that is easy to deploy and manage. The EX4200 switches are also powered by Juniper Networks Junos® operating system.

Virtual Chassis technology enables up to 10 interconnected EX4200 switches to behave and operate like a single logical device, reducing management overhead and operational expenses. Switches can be added to a Virtual Chassis configuration incrementally, as needed, delivering a scalable and energy efficient solution that doesn’t demand a large up-front investment.

Ottawa Hospital deployed Juniper Networks J Series Services Routers at the network edge. The J6350 Services Router is a modular router that’s ideal for enterprises running desktops, servers, VoIP, and enterprise applications. The Juniper routers connect the hospital to the high-speed Illinois Century Network (ICN) as well as AT&T for redundant WAN connectivity.

Juniper Networks SRX Series Services Gateways provide firewall, VPN, and intrusion prevention system (IPS) as well as antispam, antivirus, and Web filtering, protecting the hospital against known and emerging threats. Physicians and administrative staff at Ottawa Regional have secure remote access to key applications via any standard Web browser, thanks to Juniper Networks SA4500 SSL VPN Appliance. The use of SSL eliminates the need for preinstalled client software, changes to internal servers, and costly ongoing maintenance and desktop support. The SA Series provides Ottawa’s IT staff with extranet features that allow controlled access to differentiated users and groups without requiring infrastructure changes, demilitarized zone (DMZ) deployments, or software agents.

Results

One of Ottawa Regional Hospital’s biggest benefits from its new network is the ability to do more with less. With the new network the hospital increased network capacity more than 20 times from its previous infrastructure. The hospital has 10GbE links per fiber strand, which is enabled by a full 20GbE fiber ring to improve network resiliency. With J Series routers, the hospital has successfully migrated from a static routed environment to OSPF, which has improved network resiliency.

The EX Series switches gave the hospital the port density it needed to support core and edge access. It has 48 1GbE PoE ports in a compact platform on the EX Series switches. The routing infrastructure has sufficient room to grow as well, moving from supporting just one T1 to three T1s for redundancy.

Junos OS, a single network operating system that runs across Juniper Networks routing, switching, and security platforms, reduces cost and complexity, minimizes operator error, and increases reliability. Because Junos OS automates network operations in a streamlined system, Ottawa’s IT staff has more time to focus on strategic, proactive efforts.

The hospital has also been able to improve security to better comply with regulatory requirements such as the Health Information Portability and Accountability Act (HIPAA). The hospital now enjoys best-in-class enterprise network compliance security while protecting against emerging security threats. Plus, physicians and staff have secure and easy access to essential applications from anywhere, anytime, which allows the hospital to deliver better patient care.

Excerpted and reposted with permission from Juniper.net (pdf).

1. Reliable and secure Wi-Fi access. Smartphones, tablets, and wireless IP phones need the speed and stability of Wireless-N (802.11n) network access, as well as quality of service (QoS) support. Some wireless routers integrate security — such as VLANs, firewall, VPN, and security services — to increase and simplify your control.
2. Power over Ethernet (PoE). PoE juices up a network in two ways: It gives you more flexibility locating wireless access points and other wired devices, and it adds more power per port to support higher-draw technologies such as Wireless-N.
3. Stronger network security. Mobility, social networking, cloud services, and international hacking are growing. Is your security technology keeping pace? Essential technologies include content security, firewall, VPN, and VLANs. Integrated security solutions can increase application performance and give you better control.
4. Collaborative communications. Businesses can reduce operating costs and raise productivity by through unified communications and video and audio conferencing applications. Collaboration technologies demand high-performance, high-availability connections and reliable, intuitive user devices, ranging from basic IP phones to unified IP phones.
5. High-performance, high-availability connections. Businesses that use mobile devices, cloud applications, or IP voice or video require a fast and efficient traffic flow. If you want to optimize your traffic flow by investing in a new router or switch (or DNS server), it should include support for IPv6.

Recreated with permission from Cisco.com.

Contemporary network operating systems are mostly advanced and specialized branches of POSIX-compliant software platforms and are rarely developed from scratch. Generally speaking, network operating systems in routers can be traced to three generations of development, each with distinctively different architectural and design goals.

First-Generation OS: Monolithic Architecture

Typically, first-generation network operating systems for routers and switches were proprietary images running in a flat memory space. While supporting multiple processes for protocols, packet handling, and management, they operated using a cooperative, multitasking model in which each process would run to completion or until it voluntarily relinquished the CPU.

First-generation network operating systems made networking commercially viable and were deployed on a wide range of products. The downside was that these systems were plagued with a host of problems associated with resource management and fault isolation.

Second-Generation OS: Control Plane Modularity

Second-generation network operating systems are free from packet switching and thus are focused on control plane functions. Most core and edge routers installed in the past few years are running second-generation operating systems, and these systems are currently responsible for moving the bulk of traffic on the Internet and in corporate networks.

However, the lack of a software data plane in second-generation operating systems prevents them from powering low-end devices without a separate (hardware) forwarding plane. Also, some customers cannot migrate from their older software easily because of compatibility issues and legacy features still in use.

These restrictions led to the rise of transitional OS designs, in which a first-generation monolithic image would run as a process on top of the second-generation scheduler and kernel, thus bridging legacy features with newer software concepts.

Third-Generation OS: Flexibility, Scalability and Continuous Operation

Although second-generation designs were very successful, the past 10 years brought new challenges. Increased competition led to the need to lower operating expenses and a coherent case for network software flexible enough to be redeployed in network devices across the larger part of the end-to-end packet path.

Another key goal of third-generation operating systems is the capability to run with zero downtime (planned and unplanned). Third-generation operating systems also should make the migration path completely transparent to customers. They must offer an evolutionary rather than revolutionary upgrade experience typical to the retirement process of legacy software designs.

Basic OS Design Considerations

As networking vendors develop their own code, they get further and further away from the original port, not only in protocol-specific applications but also in the system area. Extensions such as control plane redundancy, in-service software upgrades and multichassis operation require significant changes on all levels of the original design. However, it is highly desirable to continue borrowing content from the donor OS in areas that are not normally the primary focus of networking vendors, such as improvements in memory management, scheduling, multicore and symmetric multiprocessing (SMP) support, and host hardware drivers.

Commercial Versus Open-Source Donor OS

The advantage of a more active and popular donor OS is not limited to just minor improvements—the cutting edge of technology creates new dimensions of product flexibility and usability. Not being locked into a single-vendor framework and roadmap enables greater control of product evolution as well as the potential to gain from progress made by independent developers.

Functional Separation and Process Scheduling

Multiprocessing, functional separation and scheduling are fundamental for almost any software design, including network software. Because CPU and memory are shared resources, all running threads and processes have to access them in a serial and controlled fashion. The next section briefly explains the intricate relation between memory, CPU cycles, system performance and stability.

Memory Model

The memory model defines whether processes (threads) run in a common memory space. If they do, the overhead for switching the threads is minimal, and the code in different threads can share data via direct memory pointers.

Scheduling Discipline

Scheduling choices are primarily between cooperative and preemptive models, which define whether thread switching happens voluntarily. A cooperative multitasking model allows the thread to run to completion, and a preemptive design ensures that every thread gets access to the CPU regardless of the state of other threads.

Virtual Memory/Preemptive Scheduling Programming Model

Virtual memory with preemptive scheduling is a great design choice for properly constructed functional blocks, where interaction between different modules is limited and well defined. This technique is one of the main benefits of the second-generation OS designs and underpins the stability and robustness of contemporary network operating systems. However, it has its own drawbacks.

Notwithstanding the overhead associated with context switching, consider the interaction between two threads, A and B, both relying on the common resource R. Because threads don’t detect their relative scheduling in the preemptive model, they can actually access R in a different order and with varying intensity.

Architecture and Infrastructure

Parallelism

Advances in multicore CPU development and the capability to run several routing processors in a system constitute the basis for increased efficiency in a router control plane. However, finding the right balance of price and performance can also be very difficult.

Flexibility and Portability

A sign of a good OS design is the capability to adapt the common software platform to various needs. The capability to extend the common operating system over several products brings the following important benefits:

• Reduced OPEX from consistent UI experience and common management interface
• Same code for all protocols; no unique defects and interoperability issues
• Common schedule for software releases; a unified feature set in the control plane
• Accelerated technology introduction; once developed, the feature ships on many platforms

Degrees of Modularity

Software modularity, as previously described, focused on the case where tasks are split into multiple loosely coupled modules. This type of modularity is called “horizontal,” as it aims at limiting dependency and mutual impact between processes operating at the same peer level. Another interesting degree of modularity is known as “vertical modularity,” where modular layers are defined between parts of the operating system in the vertical direction.

Open Architecture

An interesting implication of vertical modularity is the capability to structure code well enough to document appropriate software interfaces and allow external pluggable code. While a high degree of modularity within a system allows easy porting to different and diverse hardware architectures, a well-defined and documented application programming interface (API) can be made available to third parties for development of their own applications.

Product Maintenance

Another important characteristic of products is maintainability. It covers the process of dealing with software defects and new features, abilities to improve existing code, and the introduction of new services and capabilities. It also makes a big difference in the number and quality of NOC personnel that is required to run a network. Maintainability is where a large portion of OPEX resides.

Excerpted from Juniper.net, copyright 2010, Juniper Networks, Inc. For a more detailed look at Network Operating System Evolution, download the complete white paper here.

Related Courses
Junos Foundations: JNCIA-Junos Boot Camp (IJOS, JRE)
Junos Enterprise Routing Skills Camp (JIR, AJER)
Junos Enterprise Switching Skills Camp (JEX, AJEX)
JNCIS Enterprise Routing and Switching Certification Boot Camp (JIR, JEX)

Since it’s hard to decide which candidates are the best qualified without third-party validation (i.e., certification exams), IT workers view these titles as essential for moving ahead and gaining skill competency. Historically, it’s always been commonplace for individuals in IT to earn additional certifications in order to move up the IT ladder and obtain pay increases. Of course, the more technically knowledgeable and experienced one is, the harder the exams are. It comes down to not only knowing the content but also setting aside the time and preparation involved to successfully pass the test. With that in mind, we look at a range of IT exams that are considered the most demanding and downright scary:

The Cisco Certified Internetworking Expert (CCIE) exam is legendary for intimidating test-takers the most. The CCIE is Cisco’s highest level of certification and well-known in the IT field for being one of the hardest certifications to achieve. The test includes both a written exam (one hundred questions completed in two hours) as well as an 8-hour hands-on lab practicum. To say that the lab exam is a kind of torture test might be considered hyperbole. Yet many administrators can attest to its reputation as the ultimate brain challenge and skills assessment. Test-takers must be competent enough to configure a series of networks as well as diagnose and troubleshoot a range of simple and complex problems. The CCNA exam, Cisco’s associate-level certification, is a little less daunting yet equally challenging because it represents the next level of expertise after entry-level. Divided into a number of separate technologies, the CCNA Routing and Switching exam is a particularly tough nut to crack with problems that test installation, configuration, operation, and troubleshooting of switched networks. The test has been described as more of a marathon than a sprint. It presents a thorough assessment of networking knowledge: VLANs and Trunks? Subnetting? Frame Relays? Be prepared. Be very prepared.

Continued enterprise investment in virtualization emphasizes the importance of knowledge and experience in this area. VMware, Citrix, Red Hat, and Microsoft represent the key industry virtualization players. That said, the Citrix Certified Integration Architect (CCIA) exam may be the most daunting assessment and represents the highest level of technical proficiency that Citrix offers. The exam consists of three separate written tests, a Microsoft design exam, and a 6-hour hands-on lab. Focus on the Citrix test is not meant to downplay the rigor of the VCP-510 (vSphere5) exam offered by VMware. Few actual testing details are available due to exam rules. However, the consensus on the VCP5 test is that active skill in setup and upgrades is essential in addition to administration ability, and past vSphere exams are legendary for their level of difficulty.

The important area of security has equally challenging certifications to make sure that responsible administrators truly have expertise. The Certified Information System Security Professional (CISSP) exam places strong emphasis on knowing a wide array of security information and has a prerequisite of four years of security experience. It has similarities to a college entrance exam in its rigid testing protocol: registration at an authorized test site that doesn’t allow books, notes, or Internet access. Certification is automatically renewed after three years as long as you stay on top of the minimum Continuing Professional Education (CPE) credits and Annual Maintenance Fee (AMF). This is recommended because anything you can do to stay away from this chilling exam is advised.

The Information Technology Infrastructure Library® (ITIL) exam offers great visibility and transparency into IT service capabilities on the part of the applicant. There are four levels of certification, and the Service Manager, or master’s certification, level is the highest and most difficult. This exam assesses how well an individual can analyze and apply ITIL management concepts to new areas. The test analyzes not only theory, practice, and experience in ITIL but also communication, negotiation and presentation skills.

The Microsoft Certified Architect (MCA) is not only frightfully difficult, it’s also quite expensive. Passing this exam offers entry into an elite circle of fellow architects and, as part of the testing, it requires an in-person defense of a real-world solution predesigned by the person qualifying for the certificate. The MCA is divided into two primary paths, and, in addition to extensive pre-qualifications, the testing involves a combination of lab exams and rigorous, solution-focused interviews before a review panel of MCA-certified architects.

The importance of Unified Communications and converged IP networks as it relates to increased workforce mobility and communications is represented by the Cisco Certified Network Professional (CCNP) Voice certification exam. How hard is this test? Part of the difficulty lies in understanding the number of related exams (CUCM, CCNA, Voice) that are required to simply take the CCNP Voice exam. Certification recognizes the skill of engineers to design and implement Cisco-based Unified Communications (UC) infrastructures. To that end, the exam covers everything from gateways and IP phones/applications to router utilities and switches as well as running the Cisco UC Manager. It tests advanced UC knowledge and skills required to integrate the system into underlying network architectures to create scalable, collaborative solutions.

Finally, the Project Management Professional (PMP) exam has required intense preparation over the years and continues to intimidate even the most experienced project managers. Although the test is made up of random multiple-choice questions, no method exists for guesswork — eliminating wrong answers is not the way to pass this established exam. Thorough and absolute knowledge of project management processes is essential. On the positive side, entertaining test-preparation apps and games exist to help you fine tune your knowledge and test-taking abilities. The relatively high failure rate on first attempts confirms its status as an exam not to be taken lightly.

According to the OSI layer concept, routing, or best path selection, takes place on Layer 3 and is based on the logical address. In this post, we want to discuss some of the points in that statement.

What is Layer 3?
To make the design and troubleshooting easier and group all the vendors into a common platform to achieve compatibility and interoperability, the concept of network models was created. OSI model was one of those models, and it’s composed of seven layers, each of them playing a strict role in the data delivery process.
The Layer 3, or Network Layer, is responsible for finding the right path for the data packet to reach its destination based on Logical Addresses (means addresses not really present on the network node).

But why we do need those Logical Addresses?
Despite of the existence of physical addresses (like MAC addresses) on each of the network nodes, we still need to configure Logical Addresses even if we know that the delivery of the message is still based on that physical address. Logically you have to wonder why I do need to set an IP address for my host if frames are delivered to it based on its MAC address? Simply, the reason why you configure the IP addresses is efficient routing by constructing a database of entries that represent the node addresses in a summarized way (one network ID representative multiple nodes).

Yes, routing starts on your own PC with an Anding process that takes place to determine whether the communicating device is local or remote and defines the MAC address it will use to deliver the frame.
You can view your PC routing table by issuing the command ROUTE PRINT on your command prompt.

Why do we need routing?
Simply, because each device is only aware of the connecting networks, so it needs to discover the remote ones. And routers are those dedicated devices that play the role of handling packets sent by network nodes to fellow nodes. To succeed in this handling process, the routers have to be aware of all the distant addresses, and this is done by constructing a forwarding database called a Routing Table. That table contains the Network IDs, the path where the router can reach them (Exit Interface, Next Hop), and the cost or distance of those routes ( Metrics).

How do we achieve routing?
The achievement of the routing process is guaranteed by the existence of all the possible networks in the routing database. You may wonder how the router can learn about all these networks! In STATIC ROUTING, it’s the administrator’s job to let the routers know about remote networks by entering them manually into the routing database. Obviously this can only be done when we only have limited entries. Otherwise, in the case of a huge network, DYNAMIC ROUTING PROTOCOLS are used.

Each of those protocols calculates the network path distance (Metric) in its own way. Some use the number of routers to cross (like RIP), some use the speed of the links to cross (like OSPF), and some use the speed and delay of the links to cross (like EIGRP).

How do we determine the best path?
In the process of constructing the routing database, the router may face the issue of selection when multiple paths are proposed to it by several fellow routers. In that case, the router asks two important questions: What’s the most trusted source? And what’s the lowest distance? Obviously, and based on what we discussed earlier on how routing protocols calculate path distance, the router uses this trust preference order:

• ITSELF (connected routes)
• The Administrator (Static routes)
• EIGRP
• OSPF
• RIP routes (there are more than three dynamic routing protocols and so the preference list is much longer)

This trust preference order is called Administrative Distance.

What if the router has several possible paths to the same destination from the same routing source? Here the second question, what’s the lowest distance route, acts as a tie breaker, and a distance preference order is used based on a Metric value.

Now the final case is what if the packet received by the router matches several entries in the same database? Here a third question has to be asked: What’s the most specific entry? This is determined by the using the entry with longest prefix or matching bits.

But what if the packet matches multiple entries with the same matching bits? The router load balances the packets to the possible forwarders. Meaning that if the routers receives, let’s say, twenty packets and has four different matching paths, it will divide the load (the packets) to make the routing process faster and more efficient which results in a better network performance.