Vlan and subnets

[nabs79]

Hi

It is possible to have different VLAN with the same subnet?
Iam a little confused between VLAN and subnets

Thank you

 

[billberge]

The design I like to use the most is a 10.0.0.0/22. This allows for the most subnets and maximizes the amount of useable ip address. All of the VLAN’s on the network would have the 255.255.252.0 subnet mask but each VLAN would reside on it own unique network. You can assign any switch port access into any VLAN but you cannot assign multiple VLAN’s to the same switch port.

Example.
Subnet: 10.1.0.0 Host Range: 10.1.0.1 to 10.1.3.254 VLAN 1
Subnet: 10.1.4.0 Host Range: 10.1.4.1 to 10.1.7.254 VLAN 2
Subnet: 10.1.8.0 Host Range: 10.1.8.1 to 10.1.11.254 VLAN 3
Etc, Etc, Etc……….


So I hope I didn’t confuse you

 

[IPTnewbie]

YES.

 

[IPTnewbie]

billberge what about the "aux vlan" we have the data vlan and the voice vlan assigned on each port. if not one or the other wont work CIsco IP phone or Novell windows box. 2 vlans 1 port?????

 

[pndscm]

To get back to nabs79's question, you can't have 2 VLAN's in the same LAN on the same subnet. The router would bark at you.
You can have mulitple VLAN's on the same switch port if it is in trunk mode. If it's in access mode, I believe 1 VLAN is the max unless it connects to a phone. I have heard some people say that you can have 2 VLAN's on the same access port if you have a Voice VLAN and a data VLAN and the port is connected to an IP phone. Personally, I trunk all my ports to the IP phone. If I ever had an issue with overhead traffic across the trunk, I'd restrict it to the voice and data VLAN's. Never happened yet.

 

[IPTnewbie]

pndscm i understand better. thankyou.

 

[IPTnewbie]

2vlans r on one port in our environment but in different subnets. i understand. dif dhcp servers and everything. 7960 with

 

[astros30]

You can have both a voice vlan and data vlan on one switchport without having to trunk the port. The phone sends cdp packets to the switchport to let it know that it is a phone. The phone then knows that it is in the voice vlan and tags packets for the voice vlan.

 

[nabs79]

Thank you for all your valuable answers.