Make two SG200 swtiches four switches using vlan

[abelardocarioca]

Hi,

I have two SG200 switches which I want to divide into 2 totally independent VLANs.

My guess was that I could create a VLAN #2 and then assign  ports 1- 24 to VLAN #1 (default) and ports 25-48 to VLAN #2.

Do the same thing with the second switch.

And finally connect a cable from port 1 on switch 1 to port 1 on switch 2 and

another cable from port 25 on switch 1 to port 25 on switch 2.

For some reason, devices can bee "pinged" on the same vlan ports on switch 1 but cannot reach the devices on switch 2.

Is there any way to achieve this with SG200 switches?

Thanks

[Tom Watts]

Hi Abel, a consideration here is spanning tree. Most likely with this physical connection at least 1 port is blocking. This switch does not support Cisco PVST or IEEE MSTP (802.1s).

So for basic connectivity testing-

Switch 1/Vlan 1 -> Switch 2/Vlan1  - Does this work?

Switch 1/Vlan 2 -> Switch2/Vlan2 - Does this work?

Remove the wire between vlan 2 - Does vlan 1 work?

Replace wire to vlan 2 and remove wire between vlan 1 - Does vlan 2 work?

Do you have another exernal connection such as wireless? (turn it off)

-Tom
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[abelardocarioca]

Hi Tom,

as you mention, when disconnecting one of the phisical wires that connect either vlan, the other vlan works without problems.

Would disabling the spanning tree do the trick?

What would be the downside of doing this?

Thanks again,

Abel

[abelardocarioca]

Is it possible to leave just one wire interconnecting both switches and letting the switch manage the packets to one and other vlans being Layer2 ?

[Tom Watts]

So something you can do... if vlan 1 and vlan 2 are going to the same gateway or separate gateway, that's fine.

You may create a trunk between the switches vlan 1 untag, vlan 2 tag. Then for the most upstream switch (if your router does not use spanning tree) then you can either run 2 physical wires for each vlan to the one router or if you're splitting off using 2 routers, works just the same.

-Tom
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[abelardocarioca]

Hit Tom,

thanks again for your answer.

Just to clarify since I think I've tested something similar to what you describe and couldn't make it work.

I'm adding a driagram of what I understood from your explanation:

a) one port in switch A and one in switch B should be confirgured as "Trunk 1UP 2T" (1 untag, 2 tagged) this wire will work as trunk between the two switches

b) The rest of the ports in vlan1 (switches A & B) will be configured as Trunk 1UP (default).

c) All ports in vlan2 (switches A & B) will be configured as Trunk 2UP (or should they be 2T?).

d) One port of the Vlan1 will connect to one router and on port from vlan2 will connect to another router.

What happens with the STP configuration ? Should it be enabled?

Will the Layer 2 switch be able to resolve the vlan tagging?

[Tom Watts · Accepted solution]

This is a valid topology.

Any individual connection to the router should be vlan 1 untag and vlan 2 untag.

Any host connection for vlan 1 should be vlan 1 untag, any host connection in vlan 2 should be vlan 2 untag. The only tagging we care about is between the switches, 1u,2t trunk. Everything else is respectively untagged.

-Tom
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