Wireless Access

Occasional Contributor I

Two floors with two different subnets - any issues?

I wanted to see what guys thought... Would there be any issues with running two seperate VLANs for wireless upstairs and downstairs?



1st Floor

2st Floor


Both floors will still be connecting to the same DHCP server, but roaming between floors and will cause the user to generate a different IP's, will this be an issue? Would it be best practice to just use one large subnet for both floors?




Guru Elite

Re: Two floors with two different subnets - any issues?

You should only use one subnet.  Wireless is propagated in 3 dimensions and you do not know if a user on one floor would roam to an access point on another floor.  At minimum, that would cause a disconnection as the user switches to a different subnet, but it would not provide any benefit.  Most deployments have a single VLAN for a building, minimum to avoid this issue.  Having an entire building on the same VLAN will also deal with the waste inherent in not consuming all the ip addresses on the same VLAN.

*Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba Networks or Hewlett Packard Enterprise.*
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Frequent Contributor II

Re: Two floors with two different subnets - any issues?

Yes, it is definitely a best practise to use one VLAN within the "roaming/coverage domain". Clients will get "confused" if they roam to another VLAN. They will not renew their DHCP lease on each roam (only after a while when they detect there is no IP connectivity).


Using multiple VLAN's is also inefficient in regards of IP-planning. Roaming users will use multiple DHCP leases when roaming from VLAN A to VLAN B.


If you are using a controller-based solution you can also tunnel traffic back to the controller so you will not need to stretch the user-VLAN to the AP's.


As your user-VLAN for wireless grows make sure you enable broadcast-filtering. Broadcast packets are sent at the lowest possible 802.11 data-rate, ending up using a lot of airtime in large-scale deployments.

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Occasional Contributor I

Re: Two floors with two different subnets - any issues?

Thanks everyone for the information! I will go with 1 vlan and 1 subnet.

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