Hello! I am a student of the Department of Computer Science Information Engineering. Recently, I am learing VLAN and IEEE 802.1Q protocol, and here are two questions that confused me :
1. A packet with 802.1q VLAN tag 424 is sent out from the switch via port Gi1/0/1. Later,
the same packet is sent out again, but via port Gi1/0/2. What is the difference in 802.1q header
between the two output packets from distinct source ports?
2. Three Packets with no 802.1q VLAN tag are sent out from different end users to the
switch via ports Gi1/0/3, Gi1/0/4, Gi1/0/5, respectively. What is the difference in 802.1q
header among the three packets from distinct incoming ports?
Could anyone please help me figure out these problems? Thank you!
It seems to me that #2 borders on being a trick question. If the 3 packets (should we understand that this really means frames, since packets usually denotes layer 3 orientation while frames denotes layer 2 orientation) have no 802.1q vlan tags then how could they have 802.11 headers? Frames from users where the frame has no 802.1q tag implies that the users are connected to access ports. 802.1q headers are only applied to frames on trunk ports.
And I wonder about #1. If it is literally true that "later the same packet is sent again" then it implies that there is a loop in the topology. And certainly if it is the same frame then there can be no difference in the header.