What happen connecting 2 trunk links to un-managed switch

Installing and Using OpenWrt
1

Hi,

I am thinking to by a TP-Link unmanaged 2.5gb switch (like TL-SG105-M2
), and connect to the 2 Dynalink wrx36 router's 2.5gb ports and a Linux host.

If both wrx36's 2.5gb port is enabled with Tagged-VLANs, will the VLAN works across the 2 wrx36 + the PC ?

2

As for the switch, packages are packages. It will shovel them happily.

The Dynalink routers will be able to communicate just fine with no additional configuration on either the routers or the switch.

When it comes to the computer: It will not know what to do with those tagged packages, hence not establish any connections by default. You need to decide which vlan your computer should go into and use that very vlan on your linux computer. Just don't create a network interface on eth0 but on eth0.1 on your linux computer, or on enp0s25.1 instead of enp0s25, whatever linux flavor you use.

1 Like
3

Using VLAN tags through an unmanaged switch is not recommended. Since unmanaged switches are designed for only a single untagged network, the behavior of VLANs through these devices is undefined. Sometimes it works just fine and all the VLAN tags get passed through transparently. In other cases, the use of an unmanaged switch can cause major network problems. And there are some situations where you will have minor issues (which can sometimes be hard to troubleshoot and/or identify).

Assuming it doesn't cause any direct problems with the network in general, you need to also consider the following:

  1. There is no method to control which ports are members of each VLAN
  2. All ports are trunk ports.
  3. If you have an untagged network as part of your trunk, that untagged network is present and untagged on all ports
  4. You cannot create any access ports (i.e. a port with only one network, untagged), so if you have devices that need to be connected to an untagged network (other than the possible network in #3), you have no way to manipulate the PVID assignments
  5. If there are reasons (i.e. security, etc.) that a port/downstream device) should not include one or more of the network on your trunk, you also have no way to fix that since you have no ability to set the port VLAN memberships.
3 Likes