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Two Awesomely Awesome CCNA Challenges!

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Last updated on 03/14/2020

Welcome to this….ah, what the hell do you even call this? It’s a set of CCNA challenges for the up and coming CCNA! Note that some of this stuff stretches into the CCNP territory of difficulty, but that’s what makes it a challenge! You’ll be able to solve all of these challenges with a CCNA level of knowledge.

Let’s start with…screw it, it’s 1 AM, let’s Google for an online number generator and roll twice – once to pick my overall domain and once to pick my subobjective. What? You thought I was going to tell you the numbers I rolled and the objectives? But that would ruin the challenge of finding out what the issue is! :O Never!

…fine, I’ll give you the domain it falls under.

Let’s get right into it!

Challenge #1 – Routing Technologies (Domain 2.0)

You are a network engineer for the ABC Corporation. Bob, your fellow network engineer that’s working on his CCNA, walks up to you one day in a seemingly frustrated tone of voice and asks you “why doesn’t this in DogsOverCat’s routing table?!” He shows you a laptop with SecureCRT open and the following output:

DogsOverCats(config)#router bgp 600
DogsOverCats(config-router)#network 10.0.0.1 mask 0.0.0.0

Routers DogsOverCats and CatsSuck are fully-formed eBGP neighbors, with CatsSuck in remote-AS 601 (from DogsOverCat’s perspective). DogsOverCats has a connection to a LAN segment over GigabitEthernet0/1 that belongs to the 10.0.0.0/24 subnet. DogsOverCats has an IP of 10.0.0.1/24 on this subnet.

When you ask him why he configured a mask of 0.0.0.0, Bob says this:

Well, in EIGRP, when I do a “router eigrp 1”, I can configure a network statement that matches one specific interface and nothing else by configuring it with “network 10.0.0.1 0.0.0.0”, for instance.

Sounds like a “Bob” would say this, tbh…

You tell him that in fact, no, that’s not how that works. Upon being asked for an explanation, what do you say?

Reveal answer here!
You explain to Bob that the reason that that works in EIGRP is that EIGRP uses a wildcard mask, which is a matching mechanism. You explain that the “mask” parameter in BGP and the 32-bit number that follows is used to define a subnet mask, which has to match the interface exactly in order for the network to be considered eligible for BGP advertisement.

Onto the next one! Another dice roll! I mean…a carefully chosen exam topic…totally.

Challenge #2 – Infrastructure Services (Domain 4.0)

Fine! I’ll give you a little rest after that one. Multiple choice question incoming!

You are configuring the Hot Standby Router Protocol (HSRP) on two routers connected to a multi-access network segment through a switch to aid in first-hop redundancy for all users in the 10.1.0.0/24 subnet. You configure HSRP with the 10.1.0.254 virtual IP address. All routers are correctly configured for HSRP, with Router1 in standby and Router2 in the active state for the group belonging to the 10.1.0.254 virtual IP.

Coincidentally, two network administrators approach you, each with results for two frames. One provides you with a frame from Router1 with the MAC address 00:00:0c:9F:FB:50 and the other administrator provides you with a frame with the MAC address 00:00:0c:07:ac:B5 from Router2.

Which of the following is true based solely on the information given and no additional speculation? (Select all choices that are applicable in this problem.)

A.) Router1 is using HSRPv1 for HSRP group 2896.
B.) Router1 is using HSRPv2 for HSRP group 2896.
C.) Router1 is using HSRPv1 for HSRP group 181.
D.) Router1 is using HSRPv2 for HSRP group 181.
E.) Router2 is using HSRPv1 for HSRP group 2896.
F.) Router2 is using HSRPv2 for HSRP group 2896.
G.) Router2 is using HSRPv1 for HSRP group 181.
H.) Router2 is using HSRPv2 for HSRP group 181.

Reveal answer here!
The correct answers are B, F, and G. Here’s why.

B – Router1 is using HSRPv2 for group number 2896. Based on the information given regarding an incoming HSRP frame with the MAC address 0000.0c9f.fb50, you can deduce two things. Firstly, because the MAC starts with 0000.0c9f.fxxx, it is HSRPv2. HSRPv1 starts with 0000.0c07.acxx (xx designating group number). The second thing you can deduce is that the group number is hex B50, which translates to 2896 in decimal.

F – Router2 is participating in HSRPv2 for group 2896. For Router2 to be participating in a group with Router1, it has to share the same group, virtual IP address, and version. If Router1 is using HSRPv2 with group number 2896, so is Router2 if it wants to have any hope of being friends with it.

G – Router2 is participating HSRPv1 for HSRP group 181. The previous 2 answers can be deduced based on the first frame. The second frame adds a red herring to this problem. Routers can participate in multiple HSRP groups. Not only is Router2 participating in an HSRP group with Router1, but it’s also participating in an HSRP group with presumably another router that uses group 181 (B5 in hexadecmal) with HSRPv1. The key to this part of the answer is that you have to know that HSRPv1 and v2 allocate different amounts of bits in their MAC addresses to the group number (2 in HSRPv1 vs 3 in HSRPv2).

Was that a good rest? No? Awesome! Keep studying on and good luck on getting your CCNA before Certpocalyse date!

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