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This section provides some basic information about AWS networking that is likely to affect Charon-SSP when running in the cloud.

 NetworkManager is disabled on Charon-SSP AWS. Therefore, the interface configuration relies on ifcfg-files in /etc/sysconfig/network-scripts.

The information is not comprehensive. Please refer to the Amazon AWS documentation for up-to-date and comprehensive information.

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An automatically assigned public IP address is not persistent. Every time a instance starts, it is assigned a new public IP address. If persistent public addresses are needed, use Elastic IP addresses.

Interface Names

When looking at the instance from the AWS management console, the interface names are eth0, eth1, etc.

On instances without support for enhanced networking the Linux interface names are also eth0, eth1, etc.

However, on instances with support for enhanced networking, the names on the AWS level differ from those on the Linux level:

• The first (primary) interface is called ensX (where X is an integer denoting the interface number; example: ens5).
• When a second interface is added to a running instance, it maybe initially called eth0.
  However, the command ethtool -i eth0 shows that the enhanced network driver (ena) will be used for this interface. This interface will change its name to ensY (where Y is X+1) after restarting the instance. This means that any configuration file created for this interface must use the final name of the interface instead of eth0. Otherwise, the instance may become unreachable after a restart because there is no valid interface configuration (NetworkManager is not enabled on Charon-SSP AWS, so a configuration file must exist to configure the interface properly).

 To avoid confusion before the instance can be restarted, the new interface can be renamed to its final name using the command 
     ip link set eth0 name ensY && ip link set ensY up

Host to Guest Communication Considerations

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1. Create a configuration file (/etc/sysconfig/network-scripts/ifcfg-<interface-name>) for the second interface (if there is no configuration file for the primary interface, create it as well).
2. Set the correct interface for default route in /etc/sysconfig/network (example: GATEWAYDEV=eth0).
3. To prevent the cloud-init from resetting your custom network configurations, add the following lines to the /etc/cloud/cloud.cfg file:
   network:
  ; config: disabled
4. Restart the network.
5. Create an additional routing table (use the command: ip route add <path> dev <interface-name> table <table-id>). There must be an entry for every IP address assigned to the second interface and any other route to be used.
6. Set rules in the Routing Policy Database (use the command: ip rule add from <ip-address-of-second-interface> lookup <table-id>)
7. Create a static route file (/etc/sysconfig/network-scripts/route-<interface-name>)
8. Create a static rule file (/etc/sysconfig/network-scripts/rule-<interface-name>)

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