Changing the dhcp range for a wireless network to offer more host ip addresses

[timrichards1]

Hi all

Hoping someone can help. Our WLC sits on a subnet 192.168.5.0/24, the wireless dhcp address pool in question is 192.168.10.0/24 and we are consistently running out of ip addresses.

We would like to increase the pool to use the 192.168.11.x subnet too but are not too sure what the best way is to go about that. We were just going to go in to DHCP Scope - Edit and change the Pool End Address to 192.168.11.254 and the Netmask to 255.255.254.0 leaving the Default router set to 192.168.10.254 but have a feeling its not that easy.

Originally our WLC was configured by a member of staff who no longer works here and there are no notes for us to follow so any help would be REALLY welcome

[Flavio Miranda]

Hi

 Actually is that easy. You can change the DHCP scope mask just like you said, or you can add more scope and then you can create more dynamic interface on the WLC side. WLC will load balancing between dynamic interfaces.

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[timrichards1]

Hi Flavio

Thanks so much for your reply. We are very new to changing this type of setting and were wondering what the 'best practice' thinking was on this?

I'm thinking we will go ahead with the steps i mentioned as we will then have to go on to our asa firewall to make changes to the wireless object so that the increased subnet will maintain the access it currently has.

[Flavio Miranda]

We've been working with /22 network with no issue. There are good practices that state that smaller collision domain is better and it is true,but, considering today's network capacity, you can work with bigger collision domains.

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[RichardAtkin]

The best solution is to create multiple dynamic interfaces with /24 subnets.  Bundle them all together inside one Interface Group, then associate the Interface Group with your SSID.  Using /24s keeps the broadcast domain sizes down.  Broadcasts are sent at the lowest Mandatory data rate so even with shiny fast 4800 Access Points and 11AC clients, excessively large broadcast domains will mean lots of traffic being sent at very slow rates, which can murder your WiFi performance.

Interface groups are also pretty clever - the subnets don't need to be continuous ranges and they don't all need to be the same size - the WLC works it all out.  It even monitors the state of the subnets so if DHCP stops responding on a subnet within the Group, it will take that subnet out of circulation for a while so you're not blackholing Users.

Some reading here for you;

https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-5/config-guide/b_cg85/ports_and_interfaces.html#d158023e4319a1635