port-based vlan and tag-based vlan

What is difference between them? What i understand is

1. port-based vlan is old (before intrduce

802.3q) currently on the market every switch is tag-based vlan, Is it right?

1. port-based vlan no pvid concept and can not suuport trunk (talk between vlans)

Any opinion?

TIA, st

Haven't we already been over this? Port based VLANs are usually the way VLANs are implemented between the switch and the end system.

802.1Q is typically used between switches, in the trunk segments.

You can also support multiple VLANs on a segment without depending on the 802.1Q VLAN tag, though. Your would need some other mechanism than just the switch port number, as a way of differentiating. For example, even without a VLAN tag, you can use MAC addresses (source and destination) or you can use IP addresses (source and destination) to make VLAN decisions.

Bert

Thanks, Yes, Vlan can based on port,mac and protocols. What i like to know is switches on the market whether they still support port based vlan or not? To make things easy, the tag does not only work between swiches also works between switch to end system. Am i right? Do most vendors replace port based vlan to tag based vlan? (based on new ethernet interface chips?)

st

Oh, okay, yes, switches certainly do still support port-based VLANs. As far as I can tell, they are still the most common way to get hosts onto a particular VLAN.

Whether 802.1Q VLANs will eventually displace all port-based VLANs between hosts and switches, I'm not sure. It's possible. You'd have to start seeing VLAN IDs being provided via DHCP, for instance, or some other dynamic means, before hosts go in a big way to 802.1Q, I would think.

Bert

Thanks, Cisco support two types ethernet interface on their switches. access port and trunk port. Is the access port based on port vlan or tag vlan? The trunk port should be based on tag.

st

Access port is untagged, trunk port is tagged, would be my conclusion.

Bert

Thanks, some venders have one more interface type HYBRID port (access,trunk and hybrid ), I think Cisco does not has this type port, how can cisco support "hybrid" port function which can forward multliple untag and tag frames..

st

Thanks, some venders have one more interface type HYBRID port (access,trunk and hybrid ), I think Cisco does not has this type port, how can cisco support "hybrid" port function which can forward multliple untag and tag frames..

st

Thanks, some venders have one more interface type HYBRID port (access,trunk and hybrid ), I think Cisco does not has this type port, how can cisco support "hybrid" port function which can forward multliple untag and tag frames..

st

Should probably try a cisco news group. In principle, of course, there should be no problem. The Tag Protocol Type, 0x81-00, does not conflict with any other Type code or Length. So there should be no problem mixing up tagged and untagged frames over an Ethernet segment. I would expect that untagged frames would be sent over whatever default VLAN the switch establishes, at priority 0.

Bert

Right, untagged frames based on default vlan (or pvid),It means that only one untagged frames can forward for trunk port. How does it support multiple untagged (multiple vlan)? frames.

st

Only responding to the question "in principle." Which is to say, I don't know whether or how Cisco might do this.

In principle, a trunk link could assign frmaes to VLANs based on the

802.1Q tag and also based on other rules. For example, a trunk link could also assign untagged frames to VLANs based on MAC or IP addresses.

Bert

having 1 vlan which doesnt include a tag is part of 802.1Q spec.

this is the "native vlan" in cisco speak on a tagged interface (trunk in cisco speak again).

1 common application is where a switch is connected to an IP phone, and a port for a PC etc is in the back of the phone. Packets from the PC are not tagged, but phone packets are, and the switch can drop them into different vlans.

Exactly how these are configured and addressed varies on whether you have a switch (where a vlan number is global across the box) and a router (where vlan numbers are local to each interface).

there are loads of examples in the product manuals - go to the cisco site for the relevant device type in support and download the ones for the code version you have and read it.

The cisco docs are pretty good at explaining what the hardware / s/w can do and how, and why you might want to do that, and are all publically available.

=FD=D3=C3=CE=C4=D7=D6 -

Thanks both of you!