Managing a Cisco Internetwork Questions and Answers

Answer: C

Correct answer: Tells the router to look in NVRAM for the boot sequence

0x2102 is the normal setting. The last digit, 2, sets the boot field so that the router reads the startup configuration in NVRAM and follows any boot system commands there; the 1 in the third position ignores the break key. Contrast 0x2142, which sets the boot field to ignore NVRAM - the setting used deliberately for password recovery.

Answer: B

Correct answer: 1 and 4

show hosts displays the router’s name resolution table, which holds two kinds of entry: permanent mappings entered with ip host, and temporary entries cached from DNS lookups. It says nothing about other routers’ hostnames, nothing about which workstations may access the router, and nothing about Telnet session durations - the last of those comes from show users.

Answer: C

Correct answer: NVRAM should be erased and the router restarted.

The existing configuration is held in NVRAM, so erase startup-config followed by reload brings the router up clean, in setup mode. Erasing flash would remove the IOS itself, RAM is cleared by the reload in any case, and entering a new configuration over the old one leaves whatever was not explicitly overwritten - addresses, routes, access lists - still in place.

Answer: D

Correct answer: copy tftp flash

Loading a new image reverses the previous command: the source is the TFTP server and the destination is flash. The router will ask whether to erase flash first, which matters because a router with too little free flash cannot hold both images - and if the erase is accepted and the transfer then fails, the router is left with no IOS and must be recovered from ROM monitor.

Answer: B

Before you back up an IOS image to a laptop directly connected to a router's Ethernet port, make sure the TFTP server software is running on your laptop, that the Ethernet cable is a "crossover," and that the laptop is in the same subnet as the router's Ethernet port, and then you can use the copy flash tftp command from your laptop.

Answer: C

Correct answer: You must use the terminal monitor command.

Debug output is sent to the console by default. Over a Telnet or SSH session nothing appears until terminal monitor is issued, which mirrors console messages to that VTY line. The setting applies to the session only, so it must be repeated each time - and debugging over a remote session should be used with care, since heavy output can consume the router’s CPU.

Answer: C

Correct answer: show version

show version reports the IOS version, the platform, the uptime, the reason for the last reload, the memory fitted, and on its final line the configuration register - typically “Configuration register is 0x2102”. It is worth knowing that this single command answers several of the questions in this topic.

Answer: C

Correct answer: sh version

show version names the IOS release on its opening lines. show flash lists the image files held in flash, whose filenames usually embed the version, but that shows what is stored rather than what is running - and the two can differ if the router booted from a different image.

Answer: D

Correct answer: Ctrl+Shift+6, then X

Ctrl+Shift+6 followed by X suspends the current Telnet session and returns to the local router prompt, leaving the session open in the background. show sessions then lists the suspended sessions and typing their number resumes one, so several can be held open at once. It is the same escape sequence used to interrupt a long-running command.

Answer: C

Correct answer: All of the above

The question asks what the problem could be, and every one of the four would prevent the session. Wrong addressing or a defective serial cable break the path to the device; an access list filtering TCP 23 blocks the connection at the router; and a VTY line with no password set refuses the connection outright, answering “password required, but none set”. That last case is the one most often overlooked, because the network is working perfectly and the router still declines.