1 Rookie
•
11 Posts
0
9937
March 12th, 2021 16:00
PowerConnect 2848 what is "F" in VLAN config used for?
I've been battling with some of the shortcomings of this model (like not being able to put a management IP on anything but VLAN 1) and I've seen some weird "leakage" between VLANs.
I think one thing I saw was the result of a config mistake - a port was untagged for TWO VLANs at the same time, which shouldn't really be possible, but it had VLAN 1 and VLAN 2 both with a "U" when each respective VLAN was selected in the VLAN Membership page.
Even after fixing that, I was seeing something odd - two switches, each with only two VLANs and a single cable between them to provide management access (one is an internal network, the other is external). When looking at the dynamic address table on one switch, on the port linked to the other, I saw two MACs. I was expecting just one - the other switch, but I also saw a MAC from a different VLAN... That seems bad?
Anyhow, my original question here since the documentation only spends one sentence on this is when setting up port membership, there are 4 options: "unselected", "T" (tagged), "U" (untagged), and "F" ("The interface is denied membership to a VLAN"). What does "The interface is denied membership to a VLAN" mean? "A VLAN"? which one? Is this to explicitly block ingress or egress traffic from the selected VLAN? When is it to be used? Any examples for when it would be used?
DELL-Marco B
Moderator
•
3.8K Posts
1
March 15th, 2021 02:00
Hello,
to answer to your question, if you assign the F option, the interface is marked as Forbidden, it means that port is not able to join the VLAN even if it is was dynamically added using a protocol such as GVRP.
I hope this helps, thanks
Marco
sporkman
1 Rookie
•
11 Posts
0
March 18th, 2021 08:00
Ah, thanks. Makes sense. Is there any chance of nudging the documentation team and having some kind of clarification added to the manual? Even one sentence explaining it pertains to dynamic VLAN assigment would be incredibly helpful.
Also, found the root of one of my problems. An active port had TWO untagged VLANs active on it. I don't even know how that's possible, but selecting each VLAN in the VLAN membership page showed this port with a "U". I believe this created a bridge between the VLANs, which was probably causing all sorts of weird problems.
DELL-Marco B
Moderator
•
3.8K Posts
0
March 18th, 2021 10:00
Hello,
unfortunately we cannot modify the documentation as it has already released and it is hard to create the process to modify it.
It is possible to have multiple untagged port on an active port, but yes it is a bad design. Better to have only one VLAN if you want separate the device on that port from the other VLANs of course.
Thanks
Marco
iell
1 Rookie
•
1 Message
0
January 22nd, 2025 01:04
can i, huhu, hello
wwwww