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Sorry for asking this. I am not a network engineer, but I do plan my own network, and know a little on how things moved. But I am not familiar on the terms being used.

Now, suppose I have these topology:

Switch A

1 PC1 no VLAN, port set as VLAN 1
2 PC2 no VLAN, port not set as any VLAN
3 Hypervisor (VLAN 1 for Guest1 and VLAN 2 for Guest 2)
4 to Switch B, all VLAN.

Switch B

1. PC3 no VLAN, port set as VLAN 1
2. PC4 no VLAN, port set as VLAN 2
3. router, all VLAN.

Now, I know that PC1 can see PC3 and guest1, and PC2 would be alone, while PC4 can see Guest 2, while router can see all of them as separate network.

That is pretty basic knowledge, and very rough I think, so I am confused with the term of ingress, eggress, "access", "trunk", "tagged", and "untagged". So, can someone please explain to me what is tagged, untagged, trunk and access are in those ports?

Thank you

1 Answer 1

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You are mixing port-based and tagged VLANs, which is generally fine. It's important to understand the common terminology though:

  • a port in access mode connects a single untagged VLAN to an end device - the end device isn't VLAN aware
  • a port in trunk mode connects multiple tagged VLANs between switches, routers, sometimes servers - the devices need to be VLAN aware
  • a native VLAN is an optional, single, untagged VLAN on a trunk port
  • ingress refers to incoming frames/packets from the perspective of a specific node
  • egress refers to outgoing frames/packets from the perspective of a specific node

Accordingly, your PC ports are in access mode and your inter-switch/router/hypervisor ports are in trunk mode.

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  • Ok. So in my example, PC1, PC3 and PC4 are all access mode? While port 3 to hypervisor, port 4 at switch A, and port 3 at switch B are all trunk? Is that correct? So, when PC1 sends data, it is tagged as VLAN1, sends it to switch B via trunk, then untagged at port 1 switch B. Is that correct? So, what should I configure port 1 at switch B, the one that has PC3 connected? Tagged VLAN1 or untagged?
    – Magician
    Feb 9, 2023 at 8:31
  • I've added to my answer a bit, hope it's clear now.
    – Zac67
    Feb 9, 2023 at 8:52
  • I see.. thank you
    – Magician
    Feb 9, 2023 at 8:59

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