Providing a dedicated NIC for guest operating systems is the standard method in non-cloud environments. However, this configuration poses some challenges in cloud environments where MAC address / IP address combinations are fixed parameters set by the cloud provider.

This section will provide some information about how to configure such a setup in a cloud environment. It is not specific to one cloud provider. Hence, the descriptions may refer to different cloud providers if appropriate.

Basic Concept

The following images illustrates the basic concept when working with a dedicated network interface for the guest operating system. There are, of course, many variations depending on the specific environment.

Scenario: host and guest system have a dedicated NIC. The NIC used by the Charon host has a private and a public IP address, the NIC used by the guest system a private IP address and optionally a public IP address. The Internet and VPN gateways are only used for illustration and are not part of this example.

Please note: If the NIC dedicated to the guest OS does not have a public IP address, the guest system may still be able to access the Internet via the customer network reachable across a VPN gateway. This will depend on the customer specific network configuration. This type of connection is the recommended way to provided external network access to the guest system as the VPN ensures that traffic across a public network is encrypted.

The basic steps to implement the above configuration are as follows:

• Create a cloud instance in which the Charon host system runs.
• Add two NICs to the Charon host system. One for the Charon host and one for the guest system.
• Configure the appropriate access rules for instance and NICs.
• One NIC is dedicated to the Charon host, one to the guest system. Configure a private and public IP address for the NIC used by the Charon host. Configure a private IP address for the NIC used by the guest system (and optionally a public IP address - not recommended).
• On the Charon host, remove the private IP address from the NIC dedicated to the guest system if it was automatically configured and ensure that the interface will be enabled when the system starts.
• Assign the appropriate NIC to the guest system.
• Configure the guest system MAC address to be the same as the one of the NIC selected for the guest.
• After booting the guest system, configure the private IP originally assigned to the guest NIC by the cloud provider as the IP address of the guest Ethernet interface.
• Set the default route of the guest system to the default gateway or VPN gateway of the LAN.

Depending on firewall rules and cloud-specific security settings, the guest system should then be able to communicate with the following systems:

• The host system.
• The other systems in cloud-internal network (e.g. other guest and host systems).
• The customer internal network via a previously configured VPN gateway.
• Directly with the Internet if a public IP address was configured for the interface (not recommended).

The additional sections in this chapter show the basic configuration steps for the above example.

Please note:

• In this scenario any traffic between host and guest system (if configured with a public IP address) and external systems reachable via the Internet gateway is not encrypted by default. If this traffic runs across a public network, it is exposed to being monitored and even modified by third parties. The user is responsible for ensuring data protection conforming to the user's company security rules. It is strongly recommended to use encrypted VPN connections for any sensitive traffic.
• Guest operating systems are often old and no longer maintained by the original vendor. This means they are more easily compromised by attacks from the Internet. Therefore, direct Internet access for the guest system is not recommended.
• The actual configuration steps vary depending on the cloud environment used. The sample configuration below will have to be adapted to the specific environment.

Configuration Example

Important information:

• The example assumes that a Charon-SSP cloud-specific marketplace image is used. This means in particular:
  
  • The host system is a CentOS 7 system.
  • NetworkManager is disabled and the ifcfg-files in /etc/sysconfig/network-scripts are used to set up the configuration.
• If you use a different host operating system version, you must adapt the example accordingly.
• If you use a RHEL/CentOS 8 system, you must use NetworkManager to configure the interface. A similar procedure as the one described here can be used, but the interfaces must be under NetworkManager control and instead of restarting the network, you must restart the NetworkManager after editing the ifcfg-files. Alternatively, you can use nmcli commands to configure the connection. Please refer to your Linux documentation and manual pages for further information.
• As explained for AWS, remember that any automatically assigned public IP addresses will be removed by the cloud provider once the instance is restarted with a second NIC. Hence, on AWS Elastic IP addresses must be used.
• For Google cloud, note the following:
  
  • The default is that all interfaces are configured with IP addresses automatically by GCP services on the Linux host. Please refer to the Network Management section in the respective Getting Started guide for information on how to disable this automatic configuration.
  • Some base images used to create a Charon host instance may be configured to use /32 netmasks for additional interfaces, and only ARP requests for the default gateway are answered by Google. This can cause communication problems between Solaris and other instances on the same subnet (ARP requests are not answered). The workaround is to use static ARP entries on Solaris. Please refer to the Getting Started guide for more information. The latest images provided by Stromasys use /24 netmasks, so this point does not apply to them.
• The interface names used in this example (eth0 and eth1) may be different on your system. Please verify the names on your system and refer your cloud provider's documentation for more detail. Make sure you use the correct names!
• The example uses only a private address for the dedicated interface. If a public address is required, the basic steps for making the interface available to the guest system are the same.
• If you use the Charon Manager for the interface configuration (steps 4 and 5 of the example), use None as the interface configuration. Charon Manager will also activate the changes (step 6 in the manual example below).

Step 1: configure a second network interface on the Charon host system for use by the Solaris guest system.

The host system interface configuration must ensure that the private IP address associated with the new interface is not configured on the Linux Ethernet interface. This address will be used by the guest system.

Please note:

• The interface names used in the following section are for illustrative purposes only. Please familiarize yourself with the interface naming conventions used in your cloud environment. 

• The sample configuration assumes a CentOS 7 system and that the interface is configured outside the control of the NetworkManager.

To make the second interface usable for the Charon guest system, perform the following steps:

1. Add a second interface to your instance as described in the cloud-specific Getting Started guide and your cloud provider's documentation.
   
   
2. Log into the instance and become the root user (use: sudo -i)
   
   
3. Identify the names of the two Ethernet interfaces:
   # ip link show
   
   
4. Create an interface configuration file for the second interface (the file for the first one should exist). Example (use correct interface name for your configuration):
   # cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth1


5. Edit this file to match the characteristics of eth1 (use correct interface name for your configuration). The private IP address used for this interface will be assigned to the Solaris guest. Therefore, configure the Linux Interface without IP address, similar to the example below.
   
   Please note:
   a) On Charon-SSP instances based on cloud-specific marketplace images (CentOS 7), the NetworkManager is normally disabled. However, if the NetworkManager is enabled on such systems, the line NM_CONTROLLED=no prevents the NetworkManager from changing the configuration of the interface. If using a RHEL/CentOS 8 host system, the NM_CONTROLLED statement must be removed or set to yes.
   b) On some cloud platforms, the automatic cloud-specific configuration prevents the entries in the ifcfg-file to take effect (for example on GCP). Please refer to your cloud-provider's documentation and the Network Management section in the Getting Started Guide of your version for additional information.
   
   BOOTPROTO=none
DEVICE=eth1
NAME=eth1
ONBOOT=yes
TYPE=Ethernet
USERCTL=no
NM_CONTROLLED=no         (see note a above)


6. Restart the network:
   # systemctl restart network
Please note: Should there be an error when executing this command, kill the DHCP client process and retry the command.



Expected result of the example:

1. The system should still be reachable via eth0.
2. Interface eth1 should be up without having an IP address configured.

Please note: Make sure to use the correct interface names in use on your instance.

Step 2: add the dedicated Ethernet interface to the emulator configuration.

• Start the Charon Manager and open the configuration window for the emulated system.
• Configure the emulated system with the dedicated Ethernet interface as its interface.
• Set the MAC address to the same value as used by the host interface (the value assigned by your cloud provider).
• Save your configuration.

Step 3: configure the interface on the Solaris guest system to use the private IP assigned to the second NIC by your cloud provider.

Using the steps below, the Solaris guest system is configured to use the second NIC configured on the host system (please refer to your Solaris documentation for configuration details).

1. Boot Solaris and configure the IP address assigned to the dedicated guest NIC for the Solaris Ethernet interface as shown in the examples below:
   # ifconfig <interface-name> <private-guest-nic-ip>/<netmask up (Solaris 10 example)
or
# ifconfig <interface-name> <private-guest-nic-ip> netmask<mask> up (Solaris 2.6 example)
or
   # ipadm create-ip netX and ipadm create-addr -T static -a <private-guest-nic-ip>/<netmask> netX/v4 (Solaris 11 example)
   For Solaris versions before version 11, make permanent by editing /etc/hosts and set the new address for the systems hostname. Then edit /etc/netmask and add the netmask for the subnet-network.
   
   
2. Add default route on Solaris:
   # route add default <default-gateway-of-cloud-lan> <metric>
   Make permanent by editing /etc/defaultrouter and add the address of the gateway (use route -p for newer Solaris versions).
   
   
3. Add DNS server to Solaris
   
   1. Edit /etc/resolv.conf and add a nameserver line for the DNS server.
   2. Make sure, DNS is used for hostname translation: ensure that /etc/nsswitch.conf is configured to allow dns (in addition to files) for the hostname resolution.

For Solaris 11, please refer to the Oracle Solaris documentation.

Expected result (depending on security rules and firewalls):

1. The guest system should be able to communicate with the host system across the cloud LAN using the private IP addresses.
2. The guest system should be able to communicate directly with the Internet if the dedicated NIC has a public IP address (not recommended).

Please note: Do not forget that traffic transmitted across the Internet by the guest system is not encrypted by default. Take appropriate measures to protect your data. It is strongly recommended to protect the Solaris guest system by an appropriate firewall and security group configuration. If possible, any communication across the Internet should be encrypted (e.g., by using a VPN).