Routing question

Had to take a tech test for a job interview the other day and under the pressures of an exam-type scenario (mostly working against the clock) I wasn't sure about a couple of the Cisco questions. In this one the fact that the default route is incorrectly configured has thrown me as I couldn't think what traffic that would affect. Does ALL traffic need a correctly configured gateway?

Wasn't sure about any of them and must have got them wrong as picked A and D together even though they seem to contradict each other when I read it now.

Q1.jpg

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OctalDump

Only the traffic from B to other networks needs a default gateway. B and C can communicate since they are same network. A can send to B, but can't receive a response, since B has no valid route to A. This means that any communication where B must be able to respond to A won't work eg TCP handshake will fail, ICMP echo can't reply.

GDaines

So (A) and (D) are both yes, while (B) and (C) both no... but what about (E)? I suspect all the way up to Switch-2 at least will be fine even if Computer-B itself doesn't respond, so (E) no too? In which case me putting (A), (B) and (D) was nearly right. Fortunately for me this exam gives scores for correct answers, deducts a little for missed answers and deducts more for wrong answers, so I still scored some positive points.

pinkiaiii

was it 2 choice or 3 choice question ? since id only pick D, since if pc-a pings pc-b it would get to the router and frame would be sent towards interface that doesn't exist so time out since pc-b,c aren't directly connected to router.E wouldn't really show traffic bouncing back and forth since misconfigured ip route would lead to timeout if ip interface doesn't exist.

well maybe A would be correct as well since it shows network for pc-b,c ,E answer would get stuck at r2 since pc-c doesnt know network for pc a.

so guess A and D would be correct ones.

GDaines

pinkiaiii wrote: »

was it 2 choice or 3 choice question ?

All questions were multiple choice with 5 options. Answers could be 1, 2 or 3 correct but no indication as to how many to select each time (which would be easier I think).

Params7

Odd question because we don't really have enough information for Choice A. But assuming right default route was configured on PC A, and both routers have routes to each others LAN's, PC A will be able to send traffic to PC B. I would pick A, D as right answers. I wouldn't pick E. The traceroute also times out at the 3rd hop count.

OctalDump

Build it in Packet Tracer and see what happens. It's easy to understand an explanation for why a or b or whatever is right/wrong. What you need is to understand this from the ground up, and what concepts matter.