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QID SW750 error
#1
This question asks about the extended range of VLAN IDs and one of the "correct" answers (according to H2P) includes: "Extended range VLANs from 1006-4096 are stored in the startup configuration". Now, I have no problem with the last part of the statement that these are stored in NVRAM but I have an issue with the range 1006-4096. I brought this to their (H2P) attention and they sent two links to Cisco documents that actually state this is the correct range. However, I discovered many other documents from Cisco that state the correct range is 1006-4094, if you exclude 4095 as the reserved VLAN ID. H2P further answered my objections with the dismissive "But technically, you are correct. Perhaps different Cisco boxes have different limits. If you see such question in exam with VLAN option 1-4094 you can select it." No kidding! That's what I was going to do anyway! But what happens if BOTH ranges are on the test? Which one do we select? Why would different boxes have different ranges anyway if the VLAN ID field is limited to 12 bits? If it was extended to 13 bits that would have been mentioned in the documentation SOMEWHERE but the range would then go from 0-8191 (since two to the thirteenth power is 8092). How else can you justify including 4096 as a valid VLAN ID number? You can't.

Simply put, there are 12 bits allocated to the VLAN ID field in the 802.1q Ethernet frame, I think no one disputes that. Two to the twelfth power is 4096 which is the total number of VLAN IDs available. Now I have been taught that VLAN ID numbering starts with 0, even though that number is reserved and cannot be used. Therefore, the last number available would be 4095, NOT 4096!! Cisco documentation also states that VLAN ID 4095 is reserved and cannot be used. So here is the issue I have with H2P:

1. IF the correct extended VLAN ID range is as you state 1006-4096, then what happens to 4095? Is is still unusable or are both 4095 AND 4096 unusable?
2. How in any rational sense can you accept that 12 bits in the VLAN ID field can equate to 4097 numbers (0-4096)??? C'mon H2P, use some common sense and do't just rely on obviously wrong documentation!!
3. The answer you gave me ("But technically, you are correct. Perhaps different Cisco boxes have different limits. If you see such question in exam with VLAN option 1-4094 you can select it.") is a copout in the face of evidence to the contrary. This calls into question your willingness to admit you are wrong (despite the two documents you cited against the myriad of other documents that I can cite to the contrary) and further casts doubt as to the validity of answers to other questions you give that seem not quite right, some of which are posted in this forum.

So without a clear admission on the part of H2P that they could be wrong, that the documents they cite are wrong (typos?), and a willingness to actually change their answer accordingly I have to warn others that are looking at H2P as the tremendous help they have been at showing many how to pass Cisco exams (I count myself as one in that category), to question the validity of H2P answers and explanations. Bottom line: do NOT take their answers at face value! They are fallible just like any of us! It is the willingness to admit a mistake ("...technically, you are correct..." is no such admission but a copout in my opinion) that will increase their credibility and value. Otherwise, BEWARE!

Robert
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