Cisco Prime Access Registrar 9.0 Administrator Guide

Enhanced IP Allocation in Cisco Prime Access Registrar

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This chapter describes the enhanced IP allocation feature in Cisco Prime Access Registrar (Prime Access Registrar).

In the previous versions of Prime Access Registrar, IP allocation happens internally based on a specific range of IPs configured. If there are multiple Prime Access Registrars in a deployment, each Prime Access Registrar server will have different range of IPs configured and can allocate/de-allocate IPs only within that specific range. Prime Access Registrar cannot allocate IPs from a common pool. This is addressed by the enhanced IP allocation feature.

With this feature, IP ranges will be read from the configuration and the common IP pools will be maintained in a centralized Mongo Database (MongoDB). Any Prime Access Registrar server which is connected to the DB can allocate an available IP for a user from the common IP pools. When the user disconnects, the IP is released back to the pool again. Along with the IP pools, the user sessions will also be maintained in centralized MongoDB.

The MongoDB version used for this feature is 3.6.2.

With the enhanced IP allocation feature, IPV6 address allocation is also supported.

Note This feature is supported only in CLI.

This chapter contains the following sections:

• MongoDB Support
• IP Allocation Methodology
• Configuration Details
• Common Configuration Setup
• Sample IP Allocation Traces

MongoDB Support

This section describes the MongoDB server features:

• The centralized DB can be a single MongoDB server, a MongoDB replica set, or a MongoDB shard.
• Replica set has one primary server and two or more secondary servers. The secondary servers acts as backup servers. Prime Access Registrar supports MongoDB cluster setup, that contains multiple shards (multiple replica sets).
• MongoDB has automatic failover mechanism. If the primary goes down, the election process is triggered among the available secondary servers. The new primary is elected and it starts processing the traffic.
• The secondary DB servers can be placed in the primary DB site as well as in the geographically distant failover sites for local DB failover and site failover.

IP Allocation Methodology

With the enhanced IP allocation feature, Prime Access Registrar provides the following support:

• Dynamic allocation of IPv4 and IPv6 addresses from the common IP pool information kept in Mongo DB.
• Multiple IP pools, each with a maximum size of 16 million IPs, can be configured in Mongo DB.
• Prime Access Registrar allocates IPs from the IP pool in a fail-over manner for the incoming RADIUS and Diameter requests.
• It is possible to select and allocate IPs from one particular IP pool using the scripting point.
• Multiple Prime Access Registrar servers can be connected to the Mongo DB for the IP allocation based on the requirement.
• IP allocation/de-allocation requests can be load-balanced to any Prime Access Registrar.
• Prime Access Registrar uses compressed format to store and retrieve the IPs from DB for effective use of DB resources.
• Prime Access Registrar supports MongoDB cluster deployments to meet higher scalability needs.
• MongoDB replica set provides fail-over capabilities with the primary and secondary nodes.
• Framed-IP-Address attribute holds the allocated IP address in the Access-Accept message.

Configuration Details

In Prime Access Registrar, a new type of session manager is introduced to support this feature. This session manager can handle both RADIUS/Diameter requests coming from the RADIUS/Diameter clients respectively. All the Prime Access Registrar servers connected to the same MongoDB/MongoDB replica set/MongoDB cluster must have the same session manager configuration.

Sample IPv6 Configuration:

Sample IPv4 Configuration:

Table 11-1 lists the attributes added under /RADIUS/Advanced for the IP Allocation feature.

Common Configuration Setup

If there are multiple Prime Access Registrar servers in a deployment, common configuration must be maintained across all the servers. To maintain consistency with the configuration of all the Prime Access Registrar servers, a Python tool is developed and shipped with the Prime Access Registrar installation package. After installation, this Python tool (e.g. main.py) will be present in the /cisco-ar/bin/ directory.

Note The Python tool will not work properly, if there is a CLI access from multiple terminals.

Note Also, ensure that the correct system time is maintained across all the Prime Access Registrar servers in a deployment.

After installing Prime Access Registrar in all the identified servers, follow the below steps to maintain common configuration across all Prime Access Registrar servers:

Step 1 Set the attribute IsMaster under /r/advanced in aregcmd to TRUE.

Step 2 Perform the IP allocation configuration through aregcmd CLI interface in any one of the Prime Access Registrar servers.

Step 3 Execute SAVE from aregcmd. This creates an XML file.

Following is a sample XML file.

Step 4 Run the Python tool:

The tool will do the following:

– Prompt for the total number of Prime Access Registrar servers connected to the DB. Enter hte number.

– Convert the generated XML into a.rc file.

Following is a sample.rc file.

Step 5 Restart Prime Access Registrar. This will initialize and create the following:

– Collections in the MongoDB—These are the names of the configured session managers. These collections are created inside the DB, which is configured in mongoc data source configuration in aregcmd.

Note Make sure you do not delete the database name and collections to avoid possible data inconsistency issue.

– Required indexes in all the collections for faster access

– The DB named IPProvisioning.

Note Both the IPProvisioning database and the database configured under mongoc data source in aregcmd must have the same credentials.

– Pools in the IPProvisioning DB based on the IPAddressAllocators configuration

Step 6 Once initialization is done, the Python tool resets the IsMaster attribute to FALSE in aregcmd and prompts for the IP, credentials, etc., of the next Prime Access Registrar server. Provide the required details in the tool.

Step 7 After getting the credentials, the Python tool logs in to the new Prime Access Registrar server and dumps the.rc file generated. It also prompts you to restart the Prime Access Registrar server.

Step 8 Enter Yes and restart the Prime Access Registrar server.

Step 9 Repeat the above three steps for all the Prime Access Registrar servers. This way, configuration is maintained consistently across all individual Prime Access Registrar servers.

Sample IP Allocation Traces

Following are the sample IPv4 allocation and de-allocation traces:

Enhanced IP Allocation – Sample IPv4 Allocation Traces

Enhanced IP Allocation – Sample IPv4 De-Allocation Traces