MG21 - Limit of 4 devices in a network

[JGill]

Anyone have a large MG21 deployment?  We cannot put them in existing networks because of template issues (noted in another thread).  We planned to just create one network with all the MG21E devices so they would be easy to monitor / manage.   Except you can only put 4 MG devices in a network.  We use them as backup connections in the spare MX so they are not active unless we have a duel primary WAN failures.     Since you can carve up the /29 networks to pull from a /22 network  

Subnets:   128 
Hosts:     768

Not sure why they would limit it to 4 devices.  Anyone else run into this limitation or have a better working solution?  

Anyone for the Meraki MG product group on the forum with insights to the limitations? 

[Inderdeep]

@JGill : Well The MG cellular gateway supports NAT mode. The subnet addressing for each MG cellular gateway in LAN will be controlled by a subnet pool (referred to as the parent subnet). From this parent subnet, the dashboard will auto generate and divide the configured pool into exactly 4 children subnets. These children subnets are each assigned to the MGs available in the network. In the screenshot below, dashboard has taken the /24 parent subnet and divide them into four /26 children subnets. As it auto generate and divide into 4, so you can have only 4 MG gateways per network.

https://documentation.meraki.com/MG/MG_Wireless_WAN_Dashboard_Settings 

[JGill]

Sure, if you use the default settings.   But if you use the drop down and change it to carve up /29 from a /22 you can now have 128 networks.  Why would there be a limit of 4?  No different that when you carve up an MX template to serve up subnets.   The MG devices are standalone NAT devices, in our case, in front of an MX WAN port.  It's just another Broadband provider we don't really care what IP ranges it uses because its NAT'ed at the MX.   So sure if you care up /26 from /24 you only have 4 networks.  But if you carve up /29 from /22 you have 128 networks. 

jodies.de/ipcalc?host=172.31.128.0&mask1=24&mask2=26

Carve up as /29 (only need three IP address, gateway, primary MX, Secondary MX) and you could have 128 networks

jodies.de/ipcalc?host=172.31.128.0&mask1=22&mask2=29