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Two catalyst switches connected to each other and all ports of both are in VLAN 2. Ports that connect both switches are access ports (no Trunk) as both switches' ports are in VLAN 2, no any other VLAN. Native VLAN is still VLAN 1. So my question is how will be the control traffic? what VLAN does the control traffic use?

Control traffic = STP,CDP,DTP,VTP,PagP etc.

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    "Control" in which way? The "native VLAN" is the untagged one on a port, yet you state that VLAN 2 is used untagged (access port). Your question doesn't make much sense. – Zac67 Mar 2 at 10:25
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Since the ports that connect the switches are access ports, the concept of VLANs is meaningless. There is no tagging so there are no VLANs.

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So my question is how will be the control traffic? what VLAN does the control traffic use?

Control traffic = STP,CDP,DTP,VTP,PagP etc.

Many people say that the control traffic is in the native (untagged) VLAN for the interface, but that is really meaningless. There is no concept of VLAN for the control traffic. The control traffic uses a special MAC address that means it is link-only, never forwarded to a different interface. A VLAN is a broadcast domain, and VLAN traffic is forwarded to at least one other interface, but control traffic is not.

  • While I agree with this answer, a small clarification for the last sentence to avoid pitfalls for others. I have come across multiple "dumb switches" that don't recognize "control traffic" as anything different and forward it as normal traffic. So while that sentence is true with a better quality switch, it isn't always the case. – YLearn Mar 2 at 21:47
  • @YLearn, that is correct, but I was looking at the cisco-catalyst tag on the question for this answer. – Ron Maupin Mar 2 at 21:55

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