The 5 Hardest Topics for CCNP ROUTE Exam and how to tackle them
Certification: Cisco CCNP Routing and Switching - Cisco Certified Network Professional Routing and Switching
Cisco is, for quite some time, established as the leading company in terms of networking, and, consequently, certifying for networking. Even you, most probably, have a CISCO device somewhere in your house, especially if you have a running Wi-Fi connection, for example a router. The CCNP (Cisco Certified Network Professional) exam is used to certify that the holder has the needed knowledge and skills required to use advanced IP addressing and/or routing for implementing both scalable and secure Cisco ISR routers connected to both LANs and WANs.
So, if you want to prepare for it, what do you do? You take out the topics from the main CISCO webpage here, see what they are, make out a spreadsheet of each of them, and then try to grade yourself on how well you know each one of the subjects, then separate the ones you think are easy from those you think are hard, and start studying...but how? Those harder topics won’t be so easy to get; if they were, you probably wouldn’t be reading this.
Talking objectively, finding out which topic is harder is purely subjective. Each of us has areas he’s better at and areas he’s worse at, yet, strangely, sometimes a lot of us are worse at the same thing. And, when a lot of us are worse at that same thing, we end up considering hard, and about those statistically harder topics I will talk about. The topics themselves are EIGRP; OSPF: Link-state Advertisements and stub areas; BGP; and IPv4 and IPv6 redistribution.
What to know beforehand
Again, these are just statistically the hardest exams to tackle. It is best that you first measure up your own performances regarding these subjects before heading out to read this exam, as you may find that some topics talked about in this exam are second nature to you already.
Also, it is expected that you already have an understanding of the topics, even if at the basic level, and you possess your own reference materials and resources regarding the topics.
EIGRP isn’t actually hard in itself as much as it is rather broad. The topic covers about 25% of the exam’s questions, more than most others, maybe excluding OSPF. Most problems regarding the EIGRP topic seem to be coming from actually overthinking an otherwise simple thing. For example, most people have a hard time discerning the Advertised Distance versus the Feasible Distance concepts.
While they are both metrics and both reference distances, there are differences that are easy to spot. For one, the FD (feasible distance) references the path from a specific device, while the AD references the best path available from the neighbor-device, which usually offers the best path to the destination. For a route to get put up in the table, always remember that the potential AD must be < than the FD, so loops can be avoided.
Contrasting to the EIGRP, the OSPF is both a difficult and somewhat broad subject. Open-Short-Path-First covers, like the first, about 25% of the exam, so knowledge and proficiency over the two is a must, however the OSPF can be a little trickier, especially in two subtopics: LSAs and Stub areas.
While there are quite a lot of Link-State Protocol types, it sound a bit unreasonable to speak about all of them, as the first 5, which are the most common ones are usually the ones you need. If you do want to see all of the LSA types, you can visit our friend Wikipedia at this link.
- OSPF LSA Type 1: ROUTER LSA: Is a broadcast-type that floods its immediate area with information on the Routers and networks.
- OSPF LSA Type 2: NETWORK LSA: A designated router broadcasts to their area only what routers are joined with it in the broadcast segment.
- OSPF LSA Type 3: SUMMARY LSA: An ABR receives information about nearby networks, summarizes it, and sends it out to the other connected areas.
- OSPF LSA Type 4: ASBR-SUMMARY LSA: Helps combat problems appearing with the type 5, which may appear using type 3.
- OSPF LSA Type 5: EXTERNAL LSA: contain imported information from other routing protocols. They advertise routes that are not created within the OSPF network.
OSPF Stub Areas
LSAs themselves are not allowed everywhere in the network, and the big bad guard telling them where they can or can’t go are the stub areas. This is usually to preserve some memory and processing power, as the stub areas limit how much flooded information needs to be processed at once. There are 3 differentiable stub areas: simple Stub Areas; Totally Stubby Areas; and Not-So-Stubby Areas.
- A Stub Area accepts all LSA types except for the type 5, which goes to external routers.
- A Totally Stubby Area add restrictions on type 3 LSAs as well as type 5.
- A Not-So-Stubby Area, is mostly alike the normal Stub Area, except that, it allows for an ASBR to live, mostly undetected in the area (except by type 7 LSAs).
The idea of redistribution itself is simple. Take one network in one protocol, move it to another. Most basic example is moving an OSPF network to a EIGRP network, or the other way around. Problems arise when talking about two-way redistribution and metrics. It is easy to do, to make two different networks redistribute routes to one another, yet if a network advertises a route to the other and it has a different metric, a problem arises. More specifically, it forms a loop. While this is technically covered in the CCNP Route, it is most common for higher-level certifications.
The biggest headache with the BGP is that it has a very troublesome decision stepping process, as it requires a single best path to put up in the routing table. Thankfully, CISCO, as well as our friends at Wikipedia, provide more in-depth explanations regarding the 12-13 step process the BGP goes through to find its best path here and here, so a quick read-through of the pages should help clear things out if you know what to look for. And in case you didn’t know, you are looking for things related to: “Next hop”, weight, local preference, LIRs, AS paths, ORIGIN, MED, e/i-BGP peers, IGP, and Neighbor IP addresses. That should cover it.
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