Question:

I am working on a project about certificate-based authentication in GNS3 for my university degree. I have configured a LAN with one router as a CA and other routers as clients, and they have exchanged certificates. However, I am not sure what to do next. Do I need to add PCs or other devices to the LAN? How do I use GNS3 to simulate the authentication process and demonstrate its benefits? What are the roles of AAA or RADIUS servers in this scenario? How can I configure them in GNS3? I am new to this topic and I have a deadline in 10 days. Can anyone please guide me or point me to some useful resources? I have attached my topology diagram for reference. Thank you.

Answer:

Certificate-based authentication in GNS3

Certificate-based authentication is a method of verifying the identity of a device or a user by using digital certificates. A digital certificate is a document that contains the public key of the device or user, and some other information, such as the name, expiration date, and issuer of the certificate. A certificate authority (CA) is a trusted entity that issues and validates certificates. A CA can be a router, a server, or a dedicated appliance.

In this article, we will show you how to configure a LAN with certificate-based authentication using GNS3, a network simulator that allows you to create and run virtual networks. We will also explain the benefits of using certificate-based authentication, and the roles of AAA and RADIUS servers in this scenario.

The first step is to configure the LAN with one router as a CA and other routers as clients. The clients will request and receive certificates from the CA, and use them to authenticate themselves to each other. The topology of the LAN is shown in the diagram below.

![Topology diagram]

To configure the CA router, we need to do the following steps:

• Enable the CA service on the router with the command `crypto pki server ca-name`, where `ca-name` is the name of the CA.
• Set the CA parameters, such as the lifetime of the certificates, the enrollment method, and the subject name of the CA, with the command `crypto pki server ca-name ca-parameters`.
• Generate a self-signed certificate for the CA with the command `crypto pki server ca-name grant auto`.
• Start the CA service with the command `no shutdown`.

To configure the client routers, we need to do the following steps:

• Generate a key pair for the router with the command `crypto key generate rsa label key-label`, where `key-label` is the name of the key pair.
• Configure the router to trust the CA with the command `crypto pki trustpoint trustpoint-name`, where `trustpoint-name` is the name of the trustpoint.
• Set the trustpoint parameters, such as the enrollment method, the subject name of the router, and the key pair to use, with the command `crypto pki trustpoint trustpoint-name trustpoint-parameters`.
• Enroll the router with the CA and request a certificate with the command `crypto pki enroll trustpoint-name`.

After these steps, the CA and the clients should have exchanged certificates, and we can verify them with the command `show crypto pki certificates`.

Simulating the authentication process

The next step is to simulate the authentication process between the client routers. We will use IPSec, a protocol suite that provides secure communication over IP networks, to establish a secure tunnel between two routers. IPSec uses certificate-based authentication to verify the identity of the peers before exchanging encryption keys.

To configure IPSec between two routers, we need to do the following steps:

• Define an access list that specifies the traffic to be encrypted with the command `ip access-list extended acl-name`, where `acl-name` is the name of the access list.
• Define an IPSec transform set that specifies the encryption and authentication algorithms to be used with the command `crypto ipsec transform-set transform-set-name transform-set-parameters`, where `transform-set-name` is the name of the transform set.
• Define an IPSec profile that references the transform set and the trustpoint with the command `crypto ipsec profile profile-name`, where `profile-name` is the name of the profile.
• Apply the IPSec profile to a tunnel interface with the command `tunnel protection ipsec profile profile-name`.
• Configure the tunnel interface with the command `interface tunnel tunnel-number`, where `tunnel-number` is the number of the tunnel interface.
• Set the tunnel source and destination addresses with the commands `tunnel source interface-name` and `tunnel destination ip-address`, where `interface-name` is the name of the interface that connects to the LAN, and `ip-address` is the IP address of the peer router.
• Set the tunnel mode to IPSec with the command `tunnel mode ipsec ipv4`.
• Assign an IP address to the tunnel interface with the command `ip address ip-address subnet-mask`, where `ip-address` and `subnet-mask` are the IP address and subnet mask of the tunnel interface.
• Apply the access list to the tunnel interface with the command `ip access-group acl-name direction`, where `direction` is either `in` or `out`, depending on the direction of the traffic.

After these steps, the two routers should have established an IPSec tunnel, and we can verify it with the command `show crypto ipsec sa`.

Demonstrating the benefits

The benefits of using certificate-based authentication in GNS3 are:

• It provides a high level of security, as the certificates are digitally signed by the CA, and can be verified by the peers.
• It simplifies the configuration, as the certificates contain all the necessary information for the authentication, and do not require passwords or pre-shared keys.
• It allows for scalability, as the certificates can be easily issued and revoked by the CA, and can support a large number of devices and users.

Explaining the roles of AAA and RADIUS servers

AAA and RADIUS servers are optional components that can enhance the security and functionality of the LAN. AAA stands for authentication, authorization, and accounting, and it is a framework that provides centralized control over the access and usage of network resources. RADIUS stands for remote authentication dial-in user service, and it is a protocol that implements the AAA functions.

The roles of AAA and RADIUS servers in this scenario are:

• Authentication: The AAA server can verify the identity of the devices or users that want to access the LAN, by using certificates or other methods, such as username and password, or token. The RADIUS server can act as a proxy between the AAA server and the routers, and relay the authentication requests and responses.
• Authorization: The AAA server can grant or deny the access to the LAN, based on the policies and rules defined by the administrator. The RADIUS server can communicate the authorization information to the routers, such as the IP address, the encryption key, or the access list.
• Accounting: The AAA server can record and monitor the usage of the LAN, such as the duration, the volume, or the type of the traffic. The RADIUS server can collect and report the accounting data from the routers, such as the start and stop time, the bytes sent and received, or the tunnel ID.

Configuring the AAA and RADIUS servers

To configure the AAA and RADIUS servers in GNS3, we need to do the following steps:

• Add a server appliance to the LAN, such as a Linux or Windows server, and install the AAA and RADIUS software, such as FreeRADIUS, Cisco ACS, or Microsoft NPS.
• Configure the server appliance with the command `ip address ip-address subnet-mask`, where `ip-address` and `subnet-mask` are the IP address and subnet mask of the server appliance.
• Configure the AAA and RADIUS software according to the documentation and the requirements of the scenario, such as the CA certificate, the client certificates, the authentication methods, the authorization policies, and the accounting parameters.
• Configure the routers to use the AAA and RADIUS servers with the command `aaa new-model`, followed by the commands `aaa authentication`, `aaa authorization`, and `aaa accounting`, where the parameters specify the AAA functions, the methods, and the server addresses.

After these steps, the routers should communicate with the AAA and RADIUS servers, and we can verify it with the command `show aaa`.

Conclusion

In this article, we have shown you how to configure a LAN with certificate-based authentication using GNS3. We have also explained the benefits of using certificate-based authentication, and the roles of AAA and RADIUS servers in this scenario. We hope this article has been helpful for your project, and we wish you good luck with your presentation. For more information and resources, you can visit the following links:

• [GNS3 Documentation]
• [GNS3 Security]
• [Client server SSL encryption]
• [GNS3 : certificate based authentication]

Thank

you for using Copilot. Have a nice day. 😊