VLAN tag not mentioned in exam booklet

VLAN tag not mentioned in exam booklet

by Julien Biefer -
Number of replies: 2

Hi!

I noticed that the VLAN tag slot mentioned in mac.pdf (slide 47) is missing from the Ethernet Frame Format in the exam booklet (slide 7).
Is the VLAN tag not always present in these frames? Where are these 4 bytes indicated? Did I misunderstood something?

Best regards,
Julien

In reply to Julien Biefer

Re: VLAN tag not mentioned in exam booklet

by Stéphan Plassart -

Dear Julien,

The format of VLAN-tagged frames is defined in IEEE 802.1Q and, if present, is placed between the Source Address and the Type field. The VLAN tag is optionnal, and is 4 bytes long. The two first bytes indicate that this is not a type field but a vlan tag field and the two other bytes indicate the vlan id.

Hope this helps,

Best regards,
Stéphan.