I have a few SG300 switches and I have a bit of a problem. I'm not really sure where to look for the issue. I'm convinced it's got to do something with the config I have for our switches but let me explain the issue and see if you think the same.
We have 4 switches. They're all interconnected with LACP LAGs (two members per LAG). 3 of them connect to the main switch. There are a total of 6 VLANs assigned to each LAG trunk. We have a Sonicwall router which is connected to the main switch. We're using two physical interfaces for the router. For one of the VLANs, the router is connected via an untagged access interface. For the rest of the VLANs the router is connected via a trunk interface. And of course, the router is connected to the modem.
Now here's where the weirdness starts to happen. When transferring data from one computer to another on our local network VLAN, we get the full 1gbps regardless if it's going through multiple switches or just one. If a computer is connected directly to the main switch, we get our full internet speeds, but if a computer is connected to one of the other switches that is connected to the main switch via a LAG, the internet speed is about half (give or take) of what it should be. Internet speed is 100x20 when connected directly to the modem. We're getting anywhere from 50-80mbps on the download and 6-10 on the upload with this particular issue.
To verify that it's not our router, I created a VLAN for our WAN and plugged the modem directly to the main switch and tagged one of the LAG trunks. Sure enough, the internet speeds when connected to the other switch were the same speeds we were seeing as before. Yet we can still get the full 1gbps for other transfers.
Does that make any sense? I'm stumped. Hopefully all this came across clearly.
We are using multicast on 2 of the VLANs and IGMP snooping is enabled. Not sure if that has any significance.
