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New Member

show adjacency detail

On Ethernet links, with an 802.1q trunk, the long string of characters (below), indicate dest MAC, src MAC, 802.1q tag and the Ethertype.

sh adjacency fa1/0.200 det
Protocol Interface                 Address
IPV6     FastEthernet1/0.200       2001:200::4(5)
                                   1 packets, 114 bytes
                                   C4041FE80000C4001FE80010810000C8
                                   86DD
                                   IPv6 ND    never
                                   Epoch: 0

 

With a space between each section, these are the separate parts:

src MAC      dst MAC      802.1q   EtherType (IPv6)

C4041FE80000 C4001FE80010 810000C8 86DD

 

However - what's the significance of the leading 81 in the 802.1q portion?

 

Thanks,

Chris

Everyone's tags (1)
1 ACCEPTED SOLUTION

Accepted Solutions

It should be tag protoclol id

It should be tag protoclol id (TPID) and is used to distinguish the frame from untagged frames.

 

If you look at 802.1q header, you find a 16-bit field (TPID) set to a value of 0x8100 in order to identify the frame as an IEEE 802.1Q-tagged frame.

2 REPLIES

It should be tag protoclol id

It should be tag protoclol id (TPID) and is used to distinguish the frame from untagged frames.

 

If you look at 802.1q header, you find a 16-bit field (TPID) set to a value of 0x8100 in order to identify the frame as an IEEE 802.1Q-tagged frame.

New Member

Many Thanks. :-)

Many Thanks. :-)

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