Decode the Tag

Priority and DEI

The TCI word begins with priority and DEI bits.

highlighted = computed this step

TCI is split into smaller fields

The TCI word is 0x002a. Its first bits carry priority and DEI.

TCI=0x002a\text{TCI}=0x002a
Priority and DEIThe tag bytes are split into TPID and TCI subfields.Priority and DEI32 bits / 4 bytes0x8100002abyte 0byte 1byte 2byte 310000001000000000000000000101010tpid0x8100priorityvlan-id42priority: 0 dei: clear

Priority is zero here

The priority field is 0 in this pinned tag.

priority=0\text{priority}=0
Priority and DEIThe tag bytes are split into TPID and TCI subfields.Priority and DEI32 bits / 4 bytes0x8100002abyte 0byte 1byte 2byte 310000001000000000000000000101010tpid0x8100priorityvlan-id42priority: 0 dei: clear

DEI is clear here

The DEI bit is 0, so the strip marks it clear.

DEI=0\text{DEI}=0
Priority and DEIThe tag bytes are split into TPID and TCI subfields.Priority and DEI32 bits / 4 bytes0x8100002abyte 0byte 1byte 2byte 310000001000000000000000000101010tpid0x8100priorityvlan-id42priority: 0 dei: clear

Summary

Priority and DEI are tiny fields inside the TCI word.

0,00,0
Priority and DEIThe tag bytes are split into TPID and TCI subfields.Priority and DEI32 bits / 4 bytes0x8100002abyte 0byte 1byte 2byte 310000001000000000000000000101010tpid0x8100priorityvlan-id42priority: 0 dei: clear