VLAN-Aware switch query...

Hi All,

I have Following ambiguity regarding VLAN functionality, your answer will be really great helpful to me.

Actually, I am working on the ethernet switch which supports Packet classification engine.

Packet classification engine support VLAN-id assignment via

-programming specific pattern in the rule table.

I mean to say packet classification engine parses L2 header and L3 header, if parser out put matches with program pattern, it assign specific vlan-id (vlan-id is also programmable).

I have observed that packet classification engine assign new VLAN-ID to incoming frame (if parser output matches with program pattern) even though it is already VLAN-TAG frame.

As per standard 802.1Q ,I understood that packet classification must not assign new VLAN-ID based on packet classification engine if incoming frame is already vlan-tagged frame, I am right ? or not.

Please add your point, it would be really great support to me.

Thanks in advance Dilip

Reply to
Loading thread data ...

IEEE 802.1Q only supports VLAN assignment based on port and protocol, so this level of classification is clearly beyond the scope of the standard.

Per the standard, the bridge should always use the tag in the frame if one is already there. You can control which frames you receive from the port using "Admit Only VLAN-tagged Frames" or "Admit Only Untagged and Priority-tagged Frames" setting for the port.

Maybe the switch that you are working with is simply treating all frames it receives on that port as untagged. Does it replace the existing tag, or does it put a second tag in the frame, when forwarding

a frame that came in tagged out a port that is in the VLAN's tagged set?


Reply to

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.