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FAQ

What defines VLAN trunk modes: Unaware, C-port, S-port, and S-custom-port?

Answer:

For example, EX26262 series has four types of VLAN trunk modes (Unaware/ C-port/S-port/ S-custom-port).

  Ingress action Egress action
Unaware
The function of Unaware can be used for 802.1Q in Q (double tag).
When the port received untagged frames, an untagged frame obtain a tag (based on PVID) and is forwarded.
When the port received tagged frames,
  1. If the tagged frame with TPID=0x8100, it's become a double-tag frame, and is forwarded.
  2. If the TPID of tagged frame is not 0x8100 (ex.0x88A8), it will be discarded.
The TPID of frame transmitted by Unaware port will be set to 0x8100.
The final status of the frame after egressing are also effected by Egress Rule.
C-port When the port received untagged frames, an untagged frame obtain a tag (based on PVID) and is forwarded.
When the port received tagged frames,
  1. If a tagged frame with TPID=0x8100, it is forwarded.
  2. If the TPID of tagged frame is not 0x8100 (ex.0x88A8), it will be discarded.
The TPID of frame transmitted by C-port will be set to 0x8100.
S-port When the port received untagged frames, an untagged frame obtain a tag (based on PVID) and is forwarded.
When the port received tagged frames,
  1. If a tagged frame with TPID=0x88A8, it is forwarded.
  2. If the TPID of tagged frame is not 0x88A8 (ex.0x8100), it will be discarded.
The TPID of frame transmitted by S-port will be set to 0x88A8.
S-custom-port When the port received untagged frames, an untagged frame obtain a tag (based on PVID) and is forwarded.

When the port received tagged frames,
  1. If a tagged frame with TPID=0x88A8, it is forwarded.
  2. If the TPID of tagged frame is not 0x88A8 (ex.0x8100), it will be discarded.
The TPID of frame transmitted by S-custom-port will be set to a self-customized value, which can be set by the user using the column of Ethertype for Custom S-ports.

Port type - Ingress sample (each arrow color represents its operate behavior to individual packet)

S-custom-port is used for user defined TPID. While Ethertype for Custom S-ports is configured to 8888, outgoing packet will bring with TPID 8888 tag.