如何檢測鳥類性別

不像一般的動物，大部份鳥類都不可以從外貌去區別公母。
有些雀鳥的性別能夠透過外表去識別，例如折衷鸚鵡，公鳥是綠色，而母鳥則是紅色。




1. DNA檢測法
利用染色體的差異來鑑定性別，是較為準確的方法。
並且此方法對鳥類沒有任何不良的影響，而且對年齡没有限制。


2. 外科檢測法
從腹部切創利用內視鏡來鑑定性別，是較為有風險的方法。
此方法不適合年幼的小鳥，並且需要麻醉。

3. 糞便檢測法
利用新鮮糞便的荷爾蒙來鑑定性別
此方法安全性較高，但準確度會因應很多外來因素而有所不同，如運送及採樣過程。

Commands and applications used at layers 1 and 2

1. What would the following command allow you to do?
winipcfg

Capture events relating to data-link layer protocols
Identify a path to a destination device
View IP information for hosts running Windows 9x and Me
View the status of all connected devices and links without querying a DNS server


2. You are a network engineer working to isolate problems at the data-link layer with an end-system running a MAC OS X operating system. You want to view the path a packet takes through the network to 10.215.34.124.
What command allows you to do this?

trace 10.215.34.124
tracert [-d] 10.215.34.124
traceroute 10.215.34.124
track 1 ip route 10.215.34.124



3. Suppose you want to isolate a problem at the data-link layer by sending an echo request packet to the address www.easynomadtravel.com.
What command would allow you to do this?

arp -a
ping www.easynomadtravel.com
show ip interface brief
trace http://ｗｗｗ.easynomadtravel.com/



4. You are a network engineer working to isolate problems at the data-link layer. As part of your troubleshooting strategy, you want to view entries in the ARP table of a Cisco router.
What command allows you to do this?

arp -a
show ip arp
show ip interface brief
show arp table

Correcting physical and data-link layer problems

1. Identify the command that will allow the Cisco IOS software to return to the default LMI type on interface Serial 0/1. The LMI command is already set to the LMI type defined jointly by Cisco and three other companies.

Router(config)no frame-relay lmi-type ansi
Router(config-if)#no frame-relay lmi-type ansi
Router(config-if)#no frame-relay lmi-type cisco
Router(config-if)#no frame-relay lmi-type q933a




2. What end-system command would you use to delete a specific entry from an ARP table?

arp -a
arp -d ip-address
arp -s ip-address
arp -a -N interface_address



3. Which of the following commands activates an interface?

arp -d
clock rate
interface
no shutdown




4. What is the default encapsulation type on a synchronous serial interface?

Frame Relay
HDLC
PPP
SLIP

Physical and data-link layer support resources

1. Suppose that you are a network engineer troubleshooting a problem at the physical layer. In doing this, you want to quickly access information about the latest industry standards.
The web sites of which organizations are most likely to provide this information?

ATM Forum
IETF
ITU-T
Microsoft



2. Suppose you are troubleshooting a problem at the data-link layer. You are at the stage of evaluating and documenting the changes you are making.
If you perform a set of problem-solving steps, which are completely unsuccessful, what should you do?

You evaluate and document the changes and the results of each change that you make
You should immediately undo any changes that you have made
You make initial hardware and software configuration changes
You verify that the changes you made actually fixed the problem without introducing any new problems
You verify that you have a valid saved configuration for any device on which you intend to modify the configuration



3. Suppose you are troubleshooting a problem at the data-link layer. You are at the stage of evaluating and documenting the changes you are making and realize that the problem is intermittent.
What should be the next step you perform?

You evaluate and document the changes and the results of each change that you make
You make initial hardware and software configuration changes
You need to wait to see if the problem occurs again before you can evaluate the effect of your changes
You verify that the changes you made actually fixed the problem without introducing any new problems
You verify that you have a valid saved configuration for any device on which you intend to modify the configuration



4. As a general approach when correcting an isolated problem at the physical or data-link layer, what is the first thing you should do?

You evaluate and document the changes and the results of each change that you make
You make initial hardware and software configuration changes
You verify that the changes you made actually fixed the problem without introducing any new problems
You verify that you have a valid saved configuration for any device on which you intend to modify the configuration




5. Which website would you most likely use to find the latest detailed technical documentation about the PPP protocol?

www.apple.com
www.ietf.org
www.linux.org
www.sniffers.com

Isolating problems occurring at layers 1 and 2

1. If you encounter a line protocol down message on a router interface, what is is an indication of?

The IGRP neighbour agencies are operational on that interface
The problem lies with another router
There is a problem with the interface at the data-link layer that prevents it from functioning properly
There is a problem with the interface at the physical layer that prevents it from functioning properly



2. A group of users reports that its connection to the network has gone down due to a problem in either the physical or data-link layer. You check the operational status, errors, and configuration of the affected interfaces. You still have not found the cause of the problem.
Which guideline for isolating a problem at the physical and data-link layers have you omitted?

Checking cable configuration
Disabling Spanning Tree
Verifying the IP address of the default gateway
Viewing TCP information on a host




3. While testing your FastEthernet 0/1 interface, you have noticed some packet loss. What command should you use to isolate this problem?

debug frame-relay lmi
show interface FastEthernet 0/1
show ip interface brief
show running-config interface




4. While working on the FastEthernet 0/1 interface, you realise that it is performing poorly under load. After running a diagnostic, you discover that there are a high number of late collisions recorded. What is this an indication of?

That the duplex configuration may be mismatched
That the interface has lost its connection to the device on the other end of the Ethernet cable
That the interface has restarted itself after an error condition
That there is a problem with the interface at the data-link layer

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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