星期六, 8月 01, 2009

Identifying symptoms of problems at layers 1 and 2

1. Which command output would you most likely see if you had a problem at the physical layer?

Ethernet 0/0 is down, line protocol is down
Invalid command, no available connection
Neighbor 172.10.160.2 (Serial 1/1) is down: holding time expired
Serial 1/0 is up, line protocol is administratively down


2. Identify the true statements regarding the symptoms of data-link layer problems.

Data-link optimization problems are arguably the least common
Framing errors appear
There are large quantities of broadcast traffic
The interface is down, and the line protocol is down




3. Which command output would you most likely see if you had a problem at the data link layer?

Ethernet 0/1 is down, line protocol is down
Interface Serial 1/0, changed state to up
Serial 0/1 is down, line protocol is down
Serial 0/1 is up, line protocol is down



4. You are a network engineer working on a network experiencing problems. You use the ping command to help you isolate the problems.

Identify the ping command output that would indicate the problems are at the data-link layer of the network.

address is 0007.8580.1581
Packets: Sent = 4, Received = 2, Lost = 2 (50% loss)
Tracing route to 172.27.227.9
0 input errors, 0 CRC, 0 frame, 0 overrun



5. If you were investigating problems on the network at the physical layer, which of these would you be likely to see?

Abnormal LEDs
ARP errors
Excessive utilization
Increased buffer failures


6. What commands do you use to verify the ARP cache on a Windows end-system and the ARP table in a Cisco router?

arp -a
arp -s
show arp
show arp table
show arp ip


7. Identify the output from a traceroute that indicates the network is experiencing physical layer problems.

Excessive packet loss
Excessive runts
Increased buffer failures
Line coding errors

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