I hope someone can help with an issue I am having setting up a VLAN on a couple of our switches. I am a networking novice and this is the first time I have tried setting up a VLAN.
The VLAN I am creating is for an HDMI over IP system so will be completely separate to the default VLAN 1 used for the main school network.
The switches the HDMI Over IP system is being connected to are DLink DGS1500-28P smart switches.
I have created a new VLAN (VID:50, VLAN Name: HDMI Over IP) on both switches.
On switch 1 I have added ports 18-22 as Untagged on VLAN 50 and set these same ports as Not Member on VLAN 1.
On switch 2 I have added ports 20-22 as Untagged on VLAN 50 and set these same ports as Not Member on VLAN 1.
Both switches are connected to the core switch via port 24 however so as the HDMI Over IP system will not send data through the core switch I have run a link cable between switch 1 and 2 (using port 22 on both).
The problem occurs when I connect this link cable, before it is connected any computers connected to VLAN 1 ports can get an IP address from the server connected to the core switch with no problem, however as soon as I connect the link cable these same computers connected to VLAN 1 will no longer see the server so keep resolving a 169.234... IP address. At this point nothing else is connected to VLAN 50 except for the link cable.
This sounds spanning-tree related to me. Do you know if you're running spanning-tree on your network? If you are, I'd suggest setting these two switches to use per-vlan STP if they're not already. It could be that they're blocking port 22 for everything (just a guess). Do you have access to the switch logs?
Spanning Tree is currently disabled on these two switches (I am not sure how the core switch is setup as it was installed and configured by our local LEA IT Support team and they don't give us the passwords to access it ourselves). I am on holiday for the next week so I will try to enable it on the two Link switches then to see if it makes a difference. As this is so new to me I have attached screenshots of the configuration settings available for spanning tree, other than enabling it do I need to change any of the other settings?
You're creating a network loop by linking the two switches AND linking them to your core switch.
Is VLAN-50 tagged on port 24 of the two d-link switches? is it also tagged on your core switch?
VLAN 50 currently has port 24 set as Not Member. Other ports in the two VLANs are set as untagged, no ports are in both groups. I have just noticed that there is a Forbidden option when specifying ports (although I would of thought this would be the same as Not Member) I will give this option a try aswell when I am next in.