I have 2 vlans on a 2950, one for data and one for voice. vlan 100 data. vlan 200 voice. when I no shut the vlan 200 interface, vlan 100 interfaces gets shut down. Same thing happens when I no shut the 100 int.
I believe that Sundar is correct in identifying the problem as being that the 2950 as a layer 2 switch can have only a single VLAN "interface" active at a time.
This does not mean that the switch can have only a single VLAN active at a time, the restriction is only on VLAN interface. I find that frequently people do not understand well the distinction between having a VLAN on a switch and having a VLAN interface on a switch. The VLAN is used by the switch as part of doing the layer 2 forwarding of frames and the switch is capable of having multiple VLANs with no problem. The VLAN interface is used, as Sundar explains, for management purposes. A layer 2 switch can have only a single active VLAN interface. (A layer 3 switch can have multiple active layer 3 interfaces which it uses as part of doing its layer 3 forwarding).
So your 2950 with data VLAN and voice VLAN should be just fine. And both VLAN 100 and 200 can be used for layer 2 forwarding just fine. But it can have only 1 VLAN interface active.
I see, I have been confused on the limitation of Vlans vs. Vlan interfaces. Thanks for your help, if you would can you please have a look at my previous reply that contains some of my config, I think I am having a problem with dhcp helper.
I'm in a bit of a bind, I have a router on a stick scenario. I have a Phone and a PC on the 2950. I cant get the phone to get an address. Origionaly I was going to put ip helper on int vlan 100 and on int vlan 200.... I see that this will not work...
I find that many people do not have a good understanding of the difference between having a VLAN on a switch and having a VLAN interface on the switch. I am glad that you understand it better now.
As far as your config is concerned I have a couple of comments or suggestions:
- if the DHCP server is at 10.1.1.13 then you do need ip helper-address to forward the DHCP requests.
- you need the ip helper-address command for both VLANs. And it can be done if you put it on the router. So I suggest that you move the ip helper-address command from the switch and put it under both VLANs on the router.
- it may work to have the native VLAN configured as the physical interface on the router. But I would prefer to see it configured as a VLAN subinterface. So I would suggest that you configure this on the router:
encapsulation dot1Q 100 native
then move the ip address from the physical interface to the subinterface 100. And put ip helper-address under both of the subinterfaces on the router.
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