How does the UTM firewall assign IP address to SonicPoints (provisioning)

03/26/2020 21 13211

DESCRIPTION:
 wireless: How does the UTM firewall assign IP address to SonicPoints (provisioning)

RESOLUTION:

This article aims to provide an explanation to how the SonicPoints are provisioned with IP address.

SonicWall SonicPoints are managed (e.g. light-weighted) access points, meaning that their TCP/IP stack is not to be manually configured on the SonicPoint itself (standalone mode), but through the UTM firewall controller, which image and provisions the SonicPoints attached to a configured WLAN interface, by means of SonicWall proprietary protocols running cluster-wise between the UTM appliance and the SonicPoints theirself.*
  
The firewall SonicOS Enhanced assigns ip addresses to SonicPoints according to the following criteria:

1. The ip address pool is taken from the WLAN network configured on the interface where the SonicPoint are connected;
2. if the WLAN is segmented into VLANs, then the SonicPoint ip addresses are taken from the management network (or native VLAN);
3. The number of ip addresses reserved for the SonicPoints is determined and configurable by means of the "SonicPoint limit" parameter, which is configurable in the WLAN physical interface "General" configuration tab
4. The ip address assigned to the SonicPoints is taken from the slot: [(254 - SonicPoint_limit) - 254] belonging to the given subnet (see points 1 and 2)
Aforementioned criteria are explained next with examples and screenshots from the SonicWall SonicOS Enhanced gui.

Regarding point 1 and 2,

- the ip address pool is taken from the WLAN configured form the interface where the SonicPoint are connected;
- if the WLAN is segmented with VLANs, then the SonicPoint ip addresses are taken from the management network (or native VLAN);
if we consider the network interface configuration example in following figure:

• if a SonicPoint is connected behind X5, then it will get an ip from 10.71.205.0/24;
• if a SonicPoint is connected behind X4, then it will get an ip from 10.20.0.0/24, which is the management network or native vlan: this vlan is used only for management traffic between the firewall controller (i.e. SonicWall SonicOS Enhanced appliance) and the SonicPoints, and not used for data traffic.

Regarding point 3 and 4,

- the number of ip addresses reserved for the SonicPoints is determined and configurable by means of the "SonicPoint limit" parameter, which is configurable in the WLAN physical interface "General" configuration tab;
- the ip address assigned to the SonicPoints is taken from the slot: [(254 - SonicPoint_limit) - 254] belonging to the given subnet (see points 1 and 2);
The following example comes with the configuration tab for X4 below reported:


With the configuration in figure, recalling that the subnet of assignment is the physical interface X4, this means that:

• a maximum of 4 SonicPoints will be provisioned by the firewall controller;
• the ip addresses assigned to the 4 SonicPoints will be in the range between 10.20.0.251 - 10.20.0.254;
• the ip address assignment will start from the lower address in the range (i.e. the first SonicPoint connected will receive address  10.20.0.251);

The ip address assigned to the SonicPoints will be visible in the SonicPoint/SonicPoints page of the SonicOS gui. 
Carrying on the same example from interface X4, adding only one SonicPoint to X4, the interface will display the ip address as in the following picture:


where we can see that the SonicPoints is provisioned and operation, having the first IP address available in the slot (i.e. 10.20.0.251) 
 
*  notice that the first generation of SonicPoints (i.e. SonicPoint and SonicPoint G) can also work in standalone mode, as normal autonomous or un-managed access points, whereas SonicPoint N, Ni/Ne and N-DR works only in manager or light-weighted mode.