[Dhirendra Mandal]

How do I set an IP address limitation to control the maximum number of devices allowed to connect?

[Kartikey Mehta]

To set an IP address limitation to control the maximum number of devices allowed to connect to a network, you can use a combination of hardware and software solutions.
### **Hardware Solution**
1. **Router or Access Point Configuration**:
– **Enterprise-Grade Routers**: Use routers like Cisco Catalyst, Aruba, or Juniper Mist Access Points (e.g., AP45, AP47). These devices often include built-in features to limit connected devices by IP address allocation.
– **Steps**:
– Access the router’s admin interface (e.g., via a web browser or SSH).
– Configure the DHCP server to limit the IP address pool. For example, set a range like 192.168.1.100 to 192.168.1.110 to allow only 10 devices.
– Enable MAC address filtering to restrict access to pre-approved devices, complementing IP limitations.
– **Example Hardware**: Juniper Mist APs, as noted in the KYS Infotech post, leverage cloud-based management to enforce policies like device limits without requiring on-premises controllers.

2. **Firewall Appliances**:
– Deploy a hardware firewall (e.g., Fortinet, Palo Alto) to enforce IP-based access control lists (ACLs). ACLs can restrict the number of devices by blocking additional IP connections once a threshold is reached.
– Configure rules to monitor and cap concurrent connections.

### **Software Solution**
1. **Network Management Software**:
– Use software like Juniper Mist’s cloud platform, which supports AI-driven policy enforcement. As described in the KYS Infotech forum, Mist’s microservices architecture allows real-time monitoring and configuration of network policies, including device limits.
– **Steps**:
– Log into the management dashboard (e.g., Mist Cloud or Cisco Meraki).
– Set a policy to limit the number of devices per SSID or VLAN by restricting IP assignments.
– Use analytics to monitor connected devices and block excess connections dynamically.

2. **Open-Source Tools**:
– **pfSense**: A free, open-source firewall and router software that supports IP address limiting.
– Install pfSense on a dedicated server or VM.
– Configure the DHCP server to allocate a fixed number of IPs (e.g., 20 IPs for 20 devices).
– Use traffic shaping to prioritize or block additional devices.
– **Captive Portal**: Implement a captive portal (e.g., via pfSense or UniFi) to authenticate devices and cap connections based on user or IP limits.

3. **Scripting for Advanced Control**:
– Write scripts (e.g., Python with Scapy) to monitor ARP tables and block new IP assignments once a threshold is reached.
– Example: Use a script to check active IPs on the network and disable DHCP leases when the limit is hit.

### **Combined Approach**
– **Scenario**: For a small office with 50 devices but a limit of 20 concurrent connections:
– **Hardware**: Deploy a Juniper Mist AP connected to the Mist Cloud. Configure the DHCP pool to allocate only 20 IPs (e.g., 192.168.1.2 to 192.168.1.21).
– **Software**: Use Mist’s dashboard to set a policy limiting devices per SSID. Enable Marvis AI (as highlighted in the KYS Infotech post) to monitor and enforce the limit in real-time, alerting admins to unauthorized attempts.
– **Fallback**: Implement pfSense as a secondary check, using its captive portal to authenticate devices and ensure only 20 IPs are active.

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