In this post I will talk about the very first Alcatel-Lucent Service Routing Certification – Network Routing Specialist I (NRS I) and its corresponding exam Alcatel-Lucent Scalable IP Networks #4A0-100. I will shortly describe what is NRS I course about, and will mostly talk about what the #4A0-100 exam: what Alcatel-Lucent-specific topics you should focus on and what preparation materials to use?
Fasten your seatbelt, newcomer, you’re gonna achieve another certification soon!
What is NRS I course about?
Network Routing Specialist I course and the corresponding exam are all about networking basics and fundamentals. It’s Alcatel-Lucent’s version of Cisco CCNA R&S tailored for Service Providers field of application. And as every beginner level course it’s goal is to teach you the basics about IP networks, assuming you know nothing about it, John Snow.
Being a first step on a long journey called Service Routing Certification program, NRS I not only gives you the basic knowledge about traditional IP forwarding and switching, but also provides a bit of MPLS and VPN Services material. This effectively differs NRS I from CCNA because there will be no Enterprise related sections instead you will get a glance at Service Provider topics.
Let’s see what is actually covered in this course and exam:
- The use of the Alcatel-Lucent 7750 Service Router (SR) and the Alcatel-Lucent 7450 Ethernet Service Switch (ESS) in the Internet.
- Alcatel-Lucent SR command-line interface (CLI).
- The purpose and operations of common Layer 2 technologies.
- IP forwarding process.
- Analyzing an IP address with subnet mask and calculate subnet boundaries.
- Developing an IP address plan using IP subnetting and address summarization.
- Static routes and dynamic routing protocols basics.
- Basic configuration of static routes and dynamic routing in a single area OSPF network.
- BGP basics.
- MPLS basics.
- Introduction to MPLS-based VPN services supported on the Alcatel-Lucent 7750 SR:VPWS, VPLS, and VPRN.
As you see a lot of general topics packed into NRS I course, some of them may be familiar to you from other certification courses or educational programs, some (like MPLS) may be not. In my humble opinion this course composed very well, it has a minimum amount of historical quizzes and explanation of outdated protocols (hello, Frame Relay), rather focusing on what is actually useful for a beginner network engineer.
With this being said I’ll move forward and tell you what is the easiest way to prepare to NRS I certification exam.
NRS I certification exam
Alcatel-Lucent Scalable IP Networks #4A0-100 exam (often referred as NRS I exam) is a theoretical test lasting for 75 minutes. No vSIMs or whatsoever simulation engine, no drag&drops, just questions with 4-6 possible answers, mostly single choice. Multichoice questions always state how many answers should you choose, and this is quite handy. I do not recall how many questions were there (smth between 50-70), but you most likely wont spend more than 30 secs to give the right answer for every one of them. Read questions very carefully, its common to see questions asking you to select the FALSE statement, like “What are the FALSE characteristics of the OSPF routing protocol?”. You can’t skip questions, mark them or answer them later, every question should have its answer before proceeding to the next one.
Chances are high that you will have more than 15 minutes available after the last question, so I can’t say that this exam is a time-pressure one. Passing score is 80%. Once you pass Alcatel-Lucent Scalable IP Networks exam you will be provided with NRS I certificate issued on paper (no PDF version).
How to prepare to NRS I certification exam?
There are two “official” ways for preparation to NRS I exam
- Official 4-day long NRS I course (both remote and residential)
- Self-paced learning using Alcatel-Lucent Scalable IP Networks Self‑Study Guide.
Honestly, I don’t think that a 4-day long course would prepare you better than self-study guide (once read thoroughly). So I would recommend you to stick to self-study guide and read the whole book (in case this is your first networking certification) or go only through topics you feel you have knowledge gaps. For those who are holding networking certifications from other vendors or have basic networking skills I suggest to jump to ALU-specific questions section which covers the topics you could face in real NRS I exam.
What about practice labs?
Of course NRS I as a beginner’s course introduces you to Alcatel-Lucent’s Service Routing OS (SR OS) and its CLI, and it will certainly do no harm if you manage to get a hands-on experience with real SR OS to memorize some basic commands. Moreover, abovementioned self-study guide contains practical mini-labs to train with variety of essential configuration task like “creating logs, interface & system management, config file operations and so on). Yet, you can pass NRS I exam even if you have no Alcatel-Lucent console around, I know a bunch of engineers, who passed NRS I without hands-on experience at all (thanks to clear syntax of SROS CLI which is easy to remember).
However, its easy to get a mini-lab setup for yourself, just find vSIM *.qcow2 image of SR OS and run it with Unetlab or GNS 3 v.1.0+ under qemu/kvm emulation. Refer to these two topics on how to setup Unetlab to use with Alcatel-Lucent routers: Unetlab, Alcatel-Lucent first boot provisioning.
General topics you should pay attention to
Despite the overall easiness of this exam, there are topics you should be more than familiar with. Keeping the important things on top of the memory stack will help you to give quick answers and so spare precious minutes. At first I will cover some general topics that most likely will occur during exam session, in the next section I will point only ALU-specific topics to those of you, who know networking basics. Hereinafter I will refer to chapters and sections of Alcatel-Lucent Scalable IP Networks Self‑Study Guide to help quickly navigate to the corresponding part of the book.
Well, “Genesis of Internet” questions would arise during NRS I exam and the bad part about these questions is that you wont be able to figure out the right answer to them. You either remember the answer or you do not. So I advise you to refresh (or even memorize) your knowledge on the following subjects (Chapter 1 will shed light on these topics):
- What is ARPANET? What network replaced ARPANET later?
- How many Tiers of Service Providers are there and how do they differ?
- Who has invented the first Ethernet 10Mbit/s standard?
- What organization is responsible for public IP addresses distribution and assignment?
- What are the general differences between OSI and TCP/IP models? What stack is IS-IS protocol in?
- Which organization is now a standard body for IP area?
For sure you wont avoid questions about the general rules of switching and routing. These fundamental questions are described in Chapters 3-8 what actually makes the most part of the guide. Everything from physical medium to well-known applications (or in other words from OSI Layer 1 through Layer 7) will be presented to you through the whole book. I will point out the “most wanted” type of questions:
Physic medium and Data link questions
- What physical mediums do you know? What are their distance restrictions? Do you need fiber medium for 1Gbit Ethernet to operate?
- Basic explanation of CSMA/CD algorithm operation.
- How many Layers does ISO/OSI model have. What is the purpose of each layer? Name most popular protocols for each layer.
- Describe Full duplex and Half duplex modes of operation?
- What are the characteristics of ATM? Which ATM adaptation layer is used for transporting IP datagrams? (pay attention to ATM, you could see 1 or 2 questions about it, and they are hard-guess, you should memorize key characteristics of ATM)
- What is SONET? What speeds does SONET provide? What is STS, STM, DS and OC?
- What is PPP? Does PPP header have a fixed address field or no?
- Describe key feature of Ethernet? What fields does Ethernet header have? What error checking mechanisms does Ethernet have? Differences between Ethernet II and Ethernet 802.3?
- What are the broadcast and collision domains. Learn how to count them for a given network physical topology?
- What are the differences between hubs, switches and routers?
- Step-by-step explanation of the switching process for unicast/multicast/broadcast packets (mac learning, frame flooding) with or without VLANs configured.
- What are basic principles of STP operation? Why do Ethernet networks need it, what could happen if STP is not present?
- What problem was VLAN designed to solve? What is Q-in-Q?
Internet Protocol, addressing and subnetting, transport protocols
Besides some general topics about Layer 3 protocols, IP and addressing you should be really good in subnetting. You most likely will face more than 3 questions about subnetting and you have to do it relatively fast. An example of a subnetting question: “network address is 22.214.171.124; mask is 255.255.255.0; create 8 subnetworks”.
- Describe the key characteristics of unicast, anycast, multicast and broadcast addresses.
- Name key characteristics of IP layer. Does IP layer provide unreliable or reliable, connection-oriented or connection-less service?
- Basic principles of IP addressing:
- Who governs the global IP addressing process? What RIRs do you know?
- What is host and network portion of an address?
- What is classful and classless addressing schemes?
- What is a mask? What bit pattern represents a mask? What is VLSM?
- How to derive network and broadcast addresses from an IP address? How to derive the first/last valid host for a given network. I recommend you to use this resource – http://www.subnetting.net/Start.aspx -to practice subnetting.
- How to subnet different networks and how to aggregate them?
- What addresses are reserved for private use? Memorize them!
- What are the reserved addresses?
- Transport Layer questions. Be prepared to face a lot of questions regarding TCP/UDP operation. You should know how does TCP establish, maintain and tears down a session.
- What are the functions of Transport Layer in the OSI stack? What are the well-known Transport Protocols?
- Describe TCP protocol operation process. What is a three-way-handshake stand for? How does TCP maintain flow control, what are window size and sequence number for?
- Name key differences between UDP and TCP.
- What is a routing procedure for?
- What is Routing Table Manager (RTM) and its tasks?
- What is a preference of a route? What preference value corresponds to what routing source/protocol?
- Tell the difference between Distance Vector and Links State routing algorithms. What are the basic characteristics of these algos (speed of convergence, VLSM support, metric calculation)?
- What is static route? What is default route? How to write a static default route?
- What parameters in the OSPF Hello message should match to form an adjacency?
- What is OSPF Router ID for?
- What is the correct sequence of events in the forming of OSPF adjacency?
- What area the rules of LSA propagation? What are sequence numbers for? What will a router do upon receive LSA with a greater/lower/same Sequence Number?
- What is the well-known usage of BGP in the Internet?
- Is BGP based on Distance Vector or Link State protocol?
- What is Autonomous System? What AS numbers used for public and private AS?
- What transport protocol and port does TCP use?
- eBGP vs iBGP; what are the differences? How to tell one from another if you are presented with a topology with AS numbers assigned?
Basic network tools
- How does a ping , traceroute operate? What protocol do this tools rely on?
- Does ICMP protocol use IP protocol or it uses Layer 2 directly?
Multi-protocol Label Switching
As I mentioned earlier, NRS I introduces you to MPLS and services based on this technology. It goes without saying that you will be provided with a high-level overview, with minimum of details, just to equip you with basic understanding what is MPLS in general, what roles do routers have in MPLS domain and what services do rely on this technology? Go to Chapter 11 and absorb high-level knowledge about MPLS on 7750 SR.
Some typical questions will be posted below:
- What is Label Switch Router (LSR), Label Edge Router (LER)? What operations are performed by LSR, LER? Where do they located in MPLS domain? How do P, PE and CE routers correspond to LSR and LER?
- What is the difference between Ingress and Egress LER?
- What label PUSH, POP, SWAP operations are?
- Given the MPLS topology define Ingres/Egress LER and LSR. This question wants you to be able to point out these type of MPLS routers based on graphical representation. You should know that Ingress LER is located on the edge of non-MPLS and MPLS domains and performs Label PUSH operation on the incoming traffic. Egress LER located on the edge as well, but performs POP operation. LSR or P router located in the MPLS core and performs SWAP operation.
- What protocols are used for dynamic label assignment and propagation?
- Are MPLS labels unique across MPLS domain or router significant?
- What is Label Switched Path (LSP)?
This section is essential for those of you who wants to pass NRS I quickly and be prepared to Alcatel-Lucent-specific questions. As you might have guessed these questions are mostly about Alcatel-Lucent Service Router family (product lines positioning, hardware components, CLI commands, etc). All of these specific questions are covered in Chapter 2 of the official Alcatel-Lucent Scalable IP Networks Self‑Study Guide so please read it twice, you wont regret about this during an exam.
In the following subsections I will point out key topics you should read carefully as they are hard-to-guess since bound tightly to Alcatel-Lucent Service Routers.
7750 Service Router physical components
A vast range of specific questions are about 7750 Service Routers (7750 SR) hardware layout and components. Chapter 2 dedicated to cover this question in-depth. You should be prepared to answer for the following questions:
- What routers are present in the current line-up of 7750 SR family? How do they differ one from another?
- What are the major hardware components of a router?
- What do acronyms like CPM, CFM, IOM, MDA, IMM stand for, what are the functions of this boards and what is their position in the hardware layout?
- How many slots on SR-12 are dedicated to control processor modules (CPM)?
Data plane and Control plane overview
NRS I exam tests your ability to describe a path of a data plane and control plane traffic. Again this is explained in the Chapter 2 of the guide. Possible questions are:
- What path does a traffic take from an ingress port to an egress?
- What type of physical interfaces are available and on what board do they located?
- What is data plane/control plane for?
- What happens next after an incoming IP datagram is extracted from Layer 2 frame?
SR OS bootup process and its file system
Bootup process of a router is a complex procedure, Chapter 2 clears the whole process step-by-step and gives you detailed information about what files are included in this process and where is their default location.
- Describe a basic bootup procedure and 7750 SR file system structure.
- What are the files like boot.ldr, bof.cfg, TiMOS-m.n.Y.z, config.cfg for?
- How many flash drives (CF) does 7750 SR have? Where is runtime image stored?
- Is it possible to boot router without flash card in cf3:/ drive? Can router operate once booted without flash disk in cf3:/ drive?
Command Line Interface (CLI)
Of course you have to know your way around SR OS CLI, NRS I gives you just the basics in the Section 2.2. I, personally, find SR OS CLI very clear and straightforward, with good syntax and formatting. At this point you could find useful to have a real experience with SR OS CLI, though, as I mentioned earlier, you could memorize commands easily.
During an exam you could encounter questions which ask you about CLI contexts, particular commands and their meaning. Questions like these could arise likely:
- What are contexts of the SR OS CLI? How to navigate in and out in the tree of configuration commands?
- How to display available commands for the current configuration context? How to see a tree of available commands?
- How to autocomplete configuration commands in CLI?
- How to enter to the file system context and what are the commands here?
- How to save configuration file? Where is config.cfg file stored?
I dont have to tell you that log messages are very important. There are cases when logging is the only option to succesful troubleshoot so it is very useful to know your way around logs. Luckily it is quite easy to configure log collection on SR OS, but at first you should learn logging concept of ALU routers. Refer to the Section 2.2 and particularly to its subsection “Using Logs and Alarms” to master logging configuration. Dont skip the part with configuration steps, you may be presented with code snippet and a question about “What is wrong with this log configuration?”. Best of all would be to configure logs in CLI to get the practice and memorize the steps.
As always, I will point out some general questions which you may encounter on your exam:
- What is a severity of an event? What severities
- What log sources or streams are there on SR OS?
- What log destinations are there?
- What is log-id and what are the predefined ones (default logs)?
Link Aggregation Groups
Link aggregation concept is commonly used to provide link redundancy and bandwidth growth. LAG is Alcatel-Lucent’s version of Cisco’s EtherChannel or Juniper’s Aggregated Ethernet. Section 4.3 will provide you with everything you need on this stage to successfully answer LAG questions. Especially pay attention to what conditions should be met to combine ethernet ports into Link Aggregation Group.
- What is a LAG?
- What should be true for a LAG to become operational? What restrictions are applied to ethernet ports combined in a LAG?
- How to configure a basic LAG?
- What is port-treshold for?
- How does dynamic-cost keyword change LAG behavior?
Section 6.4 dedicated to filtering options available on 7750 SR and Service Router OS. IP Filtering also known as Access Control Lists has many areas of implementation, and NRS I focuses on the very basics. I believe that after reading my post Alcatel-Lucent. Configuring Packet (IP) Filters you wont have any troubles to answer all filter related questions in NRS I exam. Basically all you need to know is how to configure IP Filter and where you could apply it.
Interfaces and routing protocols
- What is a system interface for?
- How does Router ID for OSPF and IS-IS derive its value if not configured explicitly via router-id command?
MPLS-based VPN Services Architecture
ALU Services Architecture has similarities with other vendors implementation, but I decided to put it into ALU-specific section since it has its own flavour in most parts. Detailed coverage of Services Architecture presented in corresponding “Services Architecture” course, for NRS I exam a brief knowledge of this architecture is sufficient. You will meet with Service Access Point and Service Distribution Point paradigms unique to ALU, get a bit of basic VPN services overview such as Virtual Private Wire Service (p2p L2VPN), Virtual Private LAN Service (VPLS), Virtual Private Routed Service (VPRN or L3VPN).
Basic questions you need to be able to answer to are posted below:
- What is a VPN service in terms of virtual and private?
- How do VPN services leverage MPLS technology to isolate one service from another? What is the difference between a transport and a service label?
- What is a SAP? Is it allowed to have many SAPs on a single physical port for different services?
- What is SDP? Is it allow to bind multiple services to one SDP?
- What basic MPLS VPN services are available on 7750 SR platform?
- What are the key characteristics of VPWS, VPLS, VPRN and IES services?
- How does VPRN solves IP address overlapping issue? What is a VRF table?
- Does IES service offer “privacy” in terms of VPN services?
If you are able to answer to the most questions I posted above then you likely wont have any problems with passing Alcatel-Lucent Scalable IP Networks #4A0-100 exam. And should you have any unresolved questions (for which you cant find answers in the study guide) ask them here.