IEEE 802.1Q seems not to be terribly clear in answering this question: can a VLAN-tagged frame use LLC/SNAP encapsulation within the tagged frame?
Clause 9.4 says that a VLAN over Ethernet, i.e. which supports the Protocol Type field, uses the TPID indicating VLAN tag (which is
0x81-00).Say this is followed by the expected TCI tag, and that the CFI bit is
0 (indicating canonical format of MAC addresses). In this case, the 16- bit TCI tag is not followed by any other header extension. Simple case.Now comes the Protocol ID encapsulated within the tagged frame.
The question is, is there any reason why I can't encode that 2-byte field following the TCI tag as a length, i.e. less than 1500, and follow that with LLC header 0xAA-AA-03 and a SNAP header?
Should be legitimate, but I wanted to be sure.
Thanks.
Bert