Questions & Answers: Series 1

These are questions, I was able to answer and help others across various different social media boards.

The reason behind why I love to help others with tech/networking engineer questions is to share what I’ve learned or currently learning.

Note: Please feel free to correct me by leaving a comment below. For anonymity I will not disclose the posters name/alias. 


802.1Q frames or packets?
I'm reading the Cisco official cert guide for 350-401 after
I went through the errata and corrected all the mistakes
throughout the entire book. I'm looking at chapter one
where there is the topic of 802.1Q and VLANs.
There is a figure 1-4 displays the VLAN packet structure
which has a source/destination MAC address, other
802.1Q fields and then a source and destination IP. Then I
re-read that this is a figure of a VLAN packet. I thought
VLANs were layer two, which would be frames working off
MAC addresses and NOT IP addresses. Did I miss
something? I'm trying to recertify and this is the first I've
seen of the new exams.

By ******
Social Media: Reddit/CCNP section

My Answer

The vlan “interface” which operates at layer 3 and
provides services for the layer 2 operation.

The fundamental purpose of vlan is to limit size of broadcast domain in L2.

Yes you are correct VLAN is inherently a frame at L2.

However the VLAN interface which provides routing services to The VLAN is L3. Subsequently there’s a IP packet payload encapsulated in that sense…I hope that makes sense

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