Vlan - am I being stupid?

[jayemm]

We have an existing network, two domains Admin Curriculum, (a and c). Setup on two separate physical cables and switches.

 

I am putting one of our new switches in and want both networks available, so decided to use VLANS.

 

On new switch configured 2 ports untagged to one VLAN and two ports untagged to other. Plugged one switch into one port and one switch into other.

 

Then plugged a server with two NICs, one into each of the other ports and checked that there was a switch and a NIC connected to the different VLANs.

 

My problem is DHCP will only work if my switch is not connected to two switches.

 

I have not setup DHCP helper addresses as I am under the impression this is only if DHCP has to cross a VLAN, but in our case it doesnt.

 

Any help recieved.

[bio]

Can you explain a little further ? maybe a small drawing ? I'm not sure what you are trying to achieve here.

 

bio..

[cpjitservices]

Spanning-Tree ? See if you have Port-Fast or something similar enabled it could be something to do with spanning-tree although you have 2 cables going to the same location so it may be shutting down the ports on the switch because it will class it as a redundant link - you should be able to send all of your VLANS down the one link, also if you are going to plug in switch to switch - you need to tag the ports in which both switches are connected and you'll also need to assign the ports to the vlan which you want them to access so if you want port 1 on your switch to access VLAN 1 you'll have to assign it, if you plug your server into port one it'll be on vlan 1. I'm sure un-tagged ports will only put ports in access mode so they won't trunk the vlan's so ports need to be tagged to the ports which your switches are plugged into to switch VLAN information and traffic across the switches - You'll also need a router to route between the VLANs unless you have Layer 3 switches.

 

PS What switches are you using ?

Edited May 18, 2011 by cpjitservices

[jayemm]

Ok, figured this out in the end. The issue is that Spanning Tree was on, and it takes no notice of VLANs, hence was shutting down one of the links. Plugging into two sepperate switches has fixed this. It is only a temporary measure until we overhaul the entire server and network infrastructure over summer.

 

The VLANs were all correctly assigned, but dont want to start adding or setting up Multiple Spanning Tree.

 

JayEmm

[cpjitservices]

Thought it might of been spanning-tree - it will have shut one of those links down because Spanning-Tree would have classed it as a redundant link glad it's all sorted now - glad to be of been some help