Network Troubleshooting (24%)

N10-009 · 72 questions

• A new fiber run between two campus buildings shows link-down on both switches. The transceivers match. A visual fault locator injected at the near transceiver's transmit position is visible at the far transceiver's transmit position. Which fault does that pattern indicate?
• A warehouse handheld scanner reaches the print server on its own subnet by IP address, but IP packets to the inventory host on a different subnet never arrive. The scanner's address and prefix match the VLAN on its switch port. Which misconfiguration on the scanner explains the failure?
• A branch PC pings its default gateway, and the gateway can ping the data-center server, but the PC's ping to that server dies somewhere in between. Which tool shows the last router that still answers along the path?
• A cashier PC at a retail store shows link lights and leases 10.30.20.25 with gateway 10.30.20.1, which answers. The point-of-sale servers are on 10.30.10.0/24, and the wall port was supposed to be that sales VLAN. Which cause fits the lease the PC actually received?
• Phones at a call center play a stretch of clear audio and then a burst of clipped words. One-way delay stays near 40 milliseconds and packet loss stays near zero. Which impairment matches that pattern?
• A print-shop switch shows CRC errors climbing on one access port. The cable for that port is tied tightly along a fluorescent ballast, and moving the cable away makes the counter stop climbing. Which physical problem was the ballast causing?
• Users on a trading floor say the internal market feed stutters. The switch uplink to the feed server shows output drops climbing and utilization pinned at the interface rate. Ping loss appears only while the drops are climbing. Which problem does that pair of symptoms indicate?
• A teacher reports that the classroom display is off the network. The technician has not asked what changed this morning, what the symptom looks like, or whether any neighboring room is affected. Which step comes next?
• A server team knows a database server's MAC address and needs the access-switch port where that server is patched, without tracing cables. Which switch display answers it?
• A cable tester on a new city-hall desk run reports split pairs and high crosstalk, and gigabit will not link. The run is about 20 meters, and the pairs were untwisted and punched onto the jack. Which fault fits those results?
• Two packing stations in a warehouse take turns losing the network. Both claim the address 10.4.4.25, and the switch ARP behavior shows that address flipping between two different MAC addresses. Which fault is this?
• A new ceiling access point never powers on. Its data sheet requires 20 watts at the access point, and the switch port only offers IEEE 802.3af. Which limitation explains the dark access point?
• A technician suspects a single patch cord because one desk has no link and the switch port works with a laptop and a different cord. No cable test has been done yet. Which methodology step comes next?
• A factory branch router can ping every internal subnet listed in its routing table and cannot reach any internet address. The table contains no 0.0.0.0/0 entry. Which omission explains the internet failure?
• A hotel front-desk PC pings the reservation server by IP address and fails when the same test uses the server's name. Which tool should test the name lookup next?
• A warehouse host is addressed 10.1.1.10 with mask 255.0.0.0. It sends an ARP for 10.2.2.2 instead of forwarding that packet to its gateway. The mask should be 255.255.255.0. Why does it ARP?
• Two neighboring 2.4 GHz access points in a library use channels 1 and 2 at 20 MHz, and users near both see high retries. Which change addresses that overlap?
• A copper run to a hotel guest room measures 120 meters, and gigabit Ethernet will not stay up. The standard Ethernet channel is 100 meters. Which fault fits that measurement?
• Replication between a city agency and a site on another continent shows a steady 180-millisecond delay and almost no loss. Transfers feel slow, and loss counters stay near zero. Which impairment is this?
• A school technician theorized that a classroom cord was bad. A tester shows the cord is good, and the link is still down. Which methodology step comes next?
• An unlabeled copper drop in a school closet must be identified at the patch panel without guessing which port it uses. Which tool pair does that job?
• A warehouse switch shows CRC and input errors climbing on one uplink while the conveyor PCs are busy. Which display reports those counters for that interface?
• Two wall jacks in a school lab were patched together with a cable. Utilization on every port spikes, MAC addresses flap between ports, and spanning tree is turned off on that switch. Which fault explains it?
• A factory voice call on a rolling cart drops each time the cart moves from one access point to the next. The second radio uses a different security mode, and the two cells barely overlap. Which fault fits?
• A data-center server sends frames larger than the switch port allows. The switch counts giants, while small frames pass cleanly. Which fault matches those counters?
• At a retail store the fix is already in place, the user confirms the application works, and preventive steps have been noted. Which methodology step should the technician complete now?
• A factory switch port shut itself off after a port-security violation. Nobody had configured the port as administratively shut down. Which state is the port in, and what restores service?
• An office server answers on the admin VLAN. The office subnet has a correct route toward it, yet traceroute from an office PC stops at the firewall, and that firewall has an ACL. Which cause fits?
• A factory fiber link stays down. One end has a multimode 850 nm optic and the other end has a single-mode 1310 nm optic. Which fault is this?
• A ping from a branch office to headquarters shows about 20 percent loss, and file copies collapse under retransmissions. Delay stays modest. Which impairment is this?
• A branch hotel can reach every internal subnet in its routing table, and the internet fails. The default route is present and points at a next hop that is down. Which repair fits?
• A warehouse PC can ping its gateway and cannot ping a file server across the building. Which step should the technician take next?
• A campus technician injects a red light into a fiber, and the light shines out at a sharp bend in the tray. Which tool is in use?
• A certification tester reports near-end crosstalk failures on a short hotel run. The installer untwisted several centimeters of each pair at the jack. Which cause fits?
• Existing hotel phones keep their addresses. New phones come up with 169.254 addresses, and the DHCP scope shows zero free addresses. Which cause fits?
• Student PCs on VLAN 10 can reach each other on one campus switch, and the same VLAN dies at the uplink. The trunk's allowed list includes only VLAN 1. Which change restores VLAN 10 across that trunk?
• A library PC still reaches other hosts on its own floor, but its internet traffic is arriving at a laptop. On the PC, the gateway address is paired with a MAC that is not the router's. Which display already shows that pairing?
• A campus uses switches from several vendors. Which neighbor-discovery protocol will show the next switch's name and the port this switch is attached to?
• At the far hallway of a warehouse, laptops show a very low wireless signal, the channel has no overlap with neighboring networks, and sessions keep dropping. Which problem fits those readings?
• A retail user reports that the Wi-Fi is down and, separately, that a receipt printer is jammed. Nothing in the report links the two complaints. Which approach follows the troubleshooting method?
• Two application tiers in a data center have 10-gigabit server interfaces. The link between the tiers is 1 gigabit, that link sits at its line rate, and the server interfaces stay mostly idle. Where is the bottleneck?
• Phones on a new hotel VLAN come up with 169.254 addresses. Phones on the older VLANs still receive leases from the same DHCP server, the new scope still has free addresses, and the new router interface has no DHCP helper. Which fault is this?
• A copper run beside large factory motors shows noise on the pairs. The path cannot be moved, and the installed cable is unshielded. Which replacement addresses the noise?
• A technician at a warehouse must see whether a TCP SYN sent to the file server comes back as a SYN-ACK. Which tool shows that exchange on the wire?
• A school lab PC shows no link light. Nobody has checked the patch cord, the wall jack, or the switch port yet. Where should troubleshooting start?
• A warehouse access point is dark. The technician needs the switch's remaining PoE budget and whether that access port is actually supplying power. Which display answers both?
• Clinic PCs on VLAN 30 can ping their gateway. PCs on VLAN 40 have addresses but cannot ping the VLAN 40 gateway, and that switch virtual interface is shut down. Traffic between the VLANs fails. Which fault is this?
• A retail chain's core router has every branch prefix in its routing table except one store. There is no default route to hide the gap. That store is unreachable, and every other store works. Which fault fits?
• A new hotel desk run is 40 meters of Category 5e. The PC negotiates 1 gigabit, but a 10GBASE-T interface on that same run never establishes a 10-gigabit link. Which limitation explains it?
• A retail switch port is down, and the configuration shows an administrator shut that port on purpose. Which status is this?
• A clinic PC loads no web pages by name, yet a ping to the web server's IP address and a ping to the local gateway both succeed. The link light is on. Where should troubleshooting start?
• A data-center fiber link between two switches drops every few minutes. Both ends use matching single-mode optics. Receive power is below the optic's threshold, and one connector is dirty. Which cause fits?
• A data-center switch port shows the runt counter climbing and the giant counter staying at zero. The frames are smaller than the 64-byte Ethernet minimum. Which condition is this?
• A factory technician confirmed a theory on a lab switch: a bad uplink setting is the cause. Production has not been changed. Which methodology step comes next?
• A hotel internet circuit is sold as 500 megabits per second of capacity. During a busy evening, a successful file transfer measures about 180 megabits per second. Which term names that measured 180?
• A school will not accept a new copper run until length, wiremap, and crosstalk have been measured and passed. Which tool produces that acceptance test?
• Hotel guests in the lobby report slow Wi-Fi. The technician needs the nearby network names, the channels they use, and the signal level at that spot. Which tool shows that?
• A help desk technician at a school needs the access VLAN assigned to one switch port. Which display answers that?
• Clients on every VLAN served by one campus DHCP server receive 169.254 addresses. Each scope still has many free addresses, and the relays are configured. The server process is stopped. Which fault is this?
• Every PC in a retail VLAN received the same DHCP gateway, and that gateway address is not inside the PCs' subnet. The PCs ping each other and cannot ping the gateway. Which fault is this?
• Another access point on a school switch does not power up. The port supports PoE, the access point's draw is within what one port can supply, and the switch reports less PoE budget remaining than the access point needs. Which limit is this?
• A warehouse change that should fix the uplink was just applied on the production switch. The user has not retried the application. Which methodology step comes next?
• On a hospital floor the signal level from the access point is strong, the noise floor is also high, and clients show high retries. Neighboring radios are not on overlapping channels. Which problem is this?
• Clinic laptops are forced off an access point every few minutes. The log shows the access point sending disassociation frames. Signal is strong and channels do not overlap. Which condition is this?
• A library application fails, and the technician is logged in on the server. The technician needs to see whether the application is listening on its TCP port. Which display answers that?
• A library PC cannot reach the catalog. The technician needs the address, mask, and gateway that PC is actually using. Which display answers that?
• A hotel suspects the internet circuit is delivering less than the contracted rate. From a front-desk PC, which test measures the throughput the PC actually gets?
• A school technician has confirmed that a firewall rule is dropping the lab. The technician is not allowed to edit the firewall. Which methodology step fits?
• One member of a data-center port-channel is suspended, and its allowed VLAN list does not match the port-channel. The other member is forwarding. Which state explains the suspended member?
• A branch prefix is unreachable, and the engineer needs to see whether that prefix is installed in the edge router. Which display answers the question?
• A technician's laptop must learn whether TCP 443 is open on a clinic server. The technician cannot log in to the server. Which tool fits?
• A sensor must see a copy of the traffic on a data-center link. The switch cannot be configured for a mirror session. Which tool still provides the copy?