VLAN Tagging and Secondary Unmanaged Switches

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VLAN Tagging and Secondary Unmanaged Switches

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VLAN Tagging and Secondary Unmanaged Switches
VLAN Tagging and Secondary Unmanaged Switches
2021-10-27 22:16:21
Hardware Version: V2
Firmware Version: 1.0.9 Build 20150715 Rel.33297(s)

I have an old TL-SG3424P V2 with latest available firmware.

 

I have two VLANs (1 for management and 13 for guest traffic).

 

Mostly everything works.  Access Points are connected and setup to tag the locked network as VLAN 1 and the open (guest) network as VLAN 13.  TL-ER7206 router is at the heart of everything.

 

In one case, i have a small 5-port unmanaged switch with a PC and a copier/printer and that uplinks to a port on the SG3424P.  The computer works and can get out and can be pinged but the printer does not.  I've tried configuring the port as TRUNK (TAG is default) and as GENERAL with egress TAG.

 

I move the cable up to a port on the ER7206 and then everyone can ping the printer.  Move it back and the printer is unavailable.  Tried a different (newer unmanaged switch) between and same situation.

 

I'm not really sure why this is happening or how to troubleshoot.

 

So the above is working as long as plugged into the ER7206.  Add a Mac to one of the ports on the SG3424 and it cannot ping the printer.  Move it's connection up to the ER7206 and now it can ping the printer.

 

Something is going on in the SG3424P.  I imagine I have something configured wrong.  The ports the computer/printer and the Mac are plugged into are set with only VLAN 1.

 

Anyone have anything i can try or have any thoughts?

 

Thank you!

 

-Tim

 

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Re:VLAN Tagging and Secondary Unmanaged Switches
2021-10-27 23:18:24

It has something to do with the VLAN tagging of 1.

 

I can reproduce the problem with the connection to the ER7206.  If I turn on tagging of VLAN 1 then I can no longer ping the printer from anywhere else.

 

I probably just plain don't know what I'm doing when configuring all this...

 

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Re:VLAN Tagging and Secondary Unmanaged Switches
2021-10-28 07:22:52

@TimothyGaray 

 

The Printer could not be able to handle packets with tag, while your PC can, so the PC is fine but the printer is not.
The basic(unmanaged) switch is VLAN-transparent, so if the device behind it can't handle packets with tag, the uplink port can't be set as a tag port, need be untagged.

Just striving to develop myself while helping others.
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Re:VLAN Tagging and Secondary Unmanaged Switches
2021-10-29 02:44:15 - last edited 2021-10-29 02:46:57

@TimothyGaray 

Tagged ports = you can connect devices that support VLAN. Routers, APs, managed switches support VLAN. 

Untagged ports = regular PCs, laptops, IoT, unmanaged switches and printers. Since they don't support VLAN. They cannot process any tagged packets. They use untag. Usually, you need to set PVID on the switch VLAN config page. 

 

e.g. Port 2, you are gonna plug an unmanaged switch. Port: untagged, VLAN X(any number), PVID (same number as the VLAN)

untagged, VLAN1, PVID1

untagged, VLAN2, PVID2

so forth and so on

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