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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)

faq_ingress1.png

faq_ingress2.png

faq_ingress3.png

faq_ingress4.png

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.