CCNA v2.0 Practice Questions: Network Infrastructure and Connectivity

Correct answer: C. A damaged cable or electrical interference on the run

C is correct because both ends agree on 1000 Mb/s full duplex and there are no collisions, so CRC errors point to signal corruption on the physical path. A would show runts or late collisions and differing duplex, but both ends report full duplex. B would raise output drops, not CRC errors on received frames. D would increment the giants counter, which is zero here.

Correct answer: C. Fix the violation, then enter shutdown and no shutdown on the port

C is correct because err-disabled means a feature such as port security or BPDU guard shut the port, and it returns only after the cause is removed and the port is bounced. A describes the disabled status; an administratively shut port would show disabled, not err-disabled. B describes the notconnect status; err-disabled is a software shutdown, not a missing link. D would not help, because negotiation failures do not place a port in the err-disabled state.

Correct answer: B. No physical link, such as an unplugged or faulty cable

B is correct because notconnect means the port is enabled but detects no link partner, which matches a dark link light. A would show the status disabled rather than notconnect. C would still show connected with a link light, since VLAN membership does not affect Layer 1. D would show the status err-disabled rather than notconnect.

Correct answer: C. no shutdown

C is correct because administratively down means the interface is disabled in the configuration, and no shutdown enables it. A changes duplex negotiation but does not enable an interface that is shut down. B changes speed negotiation but does not enable an interface that is shut down. D applies to err-disabled ports, not to an interface disabled by the shutdown command.

Correct answer: B. A duplex mismatch with the server running full duplex

B is correct because late collisions on a half-duplex port with a short cable are the classic sign that the far end is transmitting in full duplex. A cannot be the cause because a 3-meter cord is far below the 100-meter limit. C would keep the link down, but the port is up at 100 Mb/s. D would raise the giants counter, which is zero.

Correct answer: C. Clean and inspect the fiber connectors and check the path for loss

C is correct because Rx power on Gi1/0/49 is flagged -- below the low alarm while the local Tx is normal, which points to loss from dirty connectors, bends or bad splices. A misreads the output, since -6.1 dBm Tx is normal and matches the healthy port. B does not address optical power, and gigabit fiber links already run full duplex. D would lower an already weak signal; attenuators fix Rx power that is too high.

Correct answer: B. Frames larger than the switch port MTU arriving from the server

B is correct because every input error is a giant, which matches jumbo frames from the server exceeding the 1500-byte switch MTU. A would raise the CRC counter, which is zero here. C describes runts, and the runts counter is zero on this full-duplex port. D would raise the overrun or ignored counters, which are zero.

Correct answer: B. Reject it; late collisions on the half-duplex end show a duplex mismatch

B is correct because SW1 is half duplex with late collisions while SW2 is full duplex with runts and CRC errors, the signature of a duplex mismatch. A misreads runts, which are undersized frames, while MTU mismatches cause giants. C ignores that the full-duplex side of a duplex mismatch also logs CRC errors and runts. D cannot explain why one end is half duplex and the other full duplex.

Correct answer: D. Accept it; Rx power exceeds the high alarm and is saturating the receiver

D is correct because the ++ flag shows +1.4 dBm above the -3.0 dBm high alarm, which a long-reach ZX optic over a short run causes and an attenuator fixes. A misreads the output, since +1.4 dBm is above every threshold rather than below the low alarm. B gets the effect backward, since an attenuator lowers received power. C reverses the problem, because ZX reaches far beyond 400 meters and the issue is too much power.

Correct answer: D. Egress congestion as gigabit traffic funnels into a 100 Mb/s port

D is correct because output drops climb with zero errors or collisions, so the port is healthy and is dropping traffic it cannot send fast enough. A would show input queue drops or overruns, which are zero. B would show CRC or output errors, and both counters are zero. C would show late collisions or CRC errors, which are all zero.