Hi there,

I have some problems with the VLAN in SwOS. On the switch is the newest version 2.13 installed.
As Router I use a RB5009UG.
I have three VLANS 1, 20 and 30 with three DHCP Servers.

I have the following configuration:
Router Port 5 VLAN 20 as Trunk --> Switch Port 15
Router Port 6 VLAN 30 as Trunk --> Switch Port 16 What is working:
When I connect my PC directly to the Port 5 or 6 of the Router and set the VLAN-ID I got the correct IP from the DHCP Server.

What doesn't work:
Whatever I set on the Switch I wont get any IP from the DHCP Server. I think I tried all possible tutorials which i have found on the Internet.
I connected my PC on the Switch to Port 18 and nothing is working.

Does somebody has an idea?

Thanks,
Cyrill

Since you're connecting switch to router using two physical connections (or even 3, how do you pass the default VLAN 1 between switch and router?), you're creating loop on physical layer. Which, if uncontrolled, can cause mayhem in your network.

STP is designed to detect and cure such case. RSTP is updated variant of it and default setup on both ROS and SwOS has it enabled. When either of them detect a loop in physical layer, they disable one of offending links. If this is happening, I'm sure sonething should be in log of router (and possibly some indication in switch). In your case this means that one of VLANs will cease to work.

There are a few ways to fix the problem:

1. use MSTP instead of RSTP.
   MSTP is VLAN-aware and in your case it wouldn't trip. I'm not sure that SwOS supports it so it may not be a feasible solution
2. use single trunk connection between router and switch, carrying all VLANs
3. if the solution above doesn't provide needed capacity, you can create a bond with multiple physical links and carry all VLANs over that bond.
   With some luck actual performance will be even better than with your currently intended setup (but might be lower as well, it all depends on traffic patterns)

Thanks for you answer.

I tried it now with the single trunk and it's working now. I will try it later with a bond, so the topic is resolved.