最近幾天準備CCNP考試，看題庫時遇到了幾道有爭議的題目，根據自己搜索的資料做了如下總結解釋：
首先是一道與VTP有關的題目：
對於選項B，相關資料表明domain names 是對大小寫敏感的，有興趣的人可以自己驗證一下。
對於選項D，官方文檔中對VTP v.1和v.2的區別描述如下：
VTP version 2 offers the following support options not available with version 1:
Unrecognized type-length-value (TLV) support—A VTP server or client propagates configuration changes to its other trunks, even for TLVs it is not able to parse. The unrecognized TLV is saved in NVRAM.
Version-dependent transparent mode—In VTP version 1, a VTP transparent switch inspects VTP messages for the domain name and version and forwards a message only if the version and domain name match. Because only one domain is supported in the Supervisor engine software, VTP version 2 forwards VTP messages in transparent mode, without checking the version.
Consistency checks—In VTP version 2, VLAN consistency checks (such as VLAN names and values) are performed only when you enter new information through the command-line interface (CLI) or Simple Network Management Protocol (SNMP). Consistency checks are not performed when new information is obtained from a VTP message or when information is read from NVRAM. If the digest on a received VTP message is correct, its information is accepted without consistency checks.
根據官方描述可以看出，對於VTP v.1中的VTP信息，transparent模式並不是不轉發，而是不僅檢測domain name而且還檢測其中的version信息，要匹配了纔會轉發，要求較嚴格，所以D選項也不準確，只能說在默認情況下，transparent 的version 爲 0，不會進行轉發。
再看E選項，乍看一下似乎是正確的，但查找了cisco官方文檔解釋說明如下：
By default all the VLANs that exist on a switch are active on a trunk link. As noted in section "6-3: Trunking", you can manually remove VLANs from a trunk link and then add them later. VTP pruning allows the switch to not forward user traffic for VLANs that are not active on a remote switch. This feature dynamically prunes unneeded traffic across trunk links. If the VLAN traffic is needed at a later date, VTP will dynamically add the VLAN back to the trunk
注意到並不是修剪掉自己的無active端口的vlan， 而是vlans that are not active on a remote switch， 所以D選項不正確
所以雖然答案給的是AD，但我只能確定A是正確的。
接下來看一道關於packet cos priority的問題，題目如下
題庫給出的順序是Voice、Call signaling、Video interactive、Video streaming、Network management、IP routing,然而查了官網的Qos（http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/QoSIntro.html）之後，可以看出真正從高到低的順序應該是Ip routing、Voice、Interactive video、Streaming Video、Call-Signaling、Network management，有個疑問就是ip routing的優先級爲什麼這麼高？難道是指的路由協議之類的控制數據流？在紅頭髮的642-813的講解視頻中的參考順序是:Voice、Interactive video、Streaming Video、Call-Signaling、Ip routing、network management。對於哪一種排序是正確的我也不太確信，只能暫時相信官方給出的優先級了。
還有一道拖圖題是對於syslog priority的問題：是要求從高到低，看了看網上其它人的說法，對於答案給的emergency、alert、critical、error、warning、notice、informational、debug，關鍵的爭議點在於是這個順序還是debug在前。查了一些資料，基本的觀點是，如果按照優先級的從高到低來排，似乎是應該把debug放在開始，也就是反過來，但是如果按照緊急程度來排的話，就應該是emergency在前，具體的問題還不是很清楚，確實有些模棱兩可的地方，就看我過幾天考交換會不會遇到這個題目了，求順利PASS