multiple subnets under one vlan

[mohammed aslam]

Hi everyone,

Is there any way to create multiple subnets under one VLAN ? Right now, I am using VLAN 110 and it's IP is 172.16.0.1/16.

We have three types of devices on this VLAN.I want to create 3 or 4 subnets for those devices under this VLAN for reducing the traffic or broadcast ?

Please advise me.....

Thanks in advance

[Peter Paluch]

Mohammed,

As long as you have a single VLAN only, you will not reduce the amount of broadcasts in this VLAN by using several IP networks. Even if the stations are in different IP networks within a single VLAN, every broadcast will be sent across the entire VLAN to all stations, regardless of their configured IP address. Broadcasting is a matter of Data Link Layer, or Layer2, and if you keep a single Layer2 domain (the VLAN), you will keep a single, merged, large broadcast domain.

Just to answer your question, you could assign multiple addresses to an interface in a single network/VLAN by using secondary IP addresses, for example:

interface Vlan110
 ip address 172.16.0.1 255.255.0.0
 ip address 192.168.1.1 255.255.255.0 secondary
 ip address 10.20.30.1 255.255.255.0 secondary

However, as I explained, this will only allow you to "stretch" multiple IP networks over a single broadcast domain so there is no saving in terms of broadcasts or traffic reduction. For that, you must resort to multiple VLANs.

Best regards,
Peter

[mohammed aslam]

Dear Peter,

First of all, Many thanks for your valuable comment.Peter, Actually what I want is create a segment for three wireless devices in a network. All are in 172.16.0.1/16 range.As you told me, it won't allow to reduce broadcast even if i create multiple IP subnets under same VLAN. So you recommend to create a multiple vlans, right ?

I can create multiple vlan but if i do it, How can i distribute those new IP.Since the access point is connected to wireless VLAN (172.16.0.1/16).So it will distribute only this range. Can we add only one port to one VLAN ?

My requirement is given below:-

We have three devices Laptops, Ipads and Apple TV. All are wireless devices and it's 172.16.0.1/16 range at the moment.

I want to create three network for these devices.I don't want to communicate these 3 network communicate each other.If i create 3 vlan, How can i distribute three ranges of IP addresses through one wireless devices or one switch port ?

Best Regards,

Mohammed