Basic Networking


Step-by-step instructions for getting started with Chameleon are available in the Getting started section of this documentation. These instructions include using basic networking functionality.

Shared Network

All Chameleon Projects have access to the fixed network sharednet1 which is used by most experiments. The sharednet1 is a pre-configured network shared among all Chameleon Projects with one Subnet and includes a Router providing NAT access to the public Internet. All instances using sharednet1 can communicate directly.

Multiple Networks

Some Chameleon bare metal nodes support connecting to multiple networks. Currently, the number of networks allowed is limited to the number of enabled NICs on the node (currently this is up to 2). It is possible to find such nodes via Resource discovery by filtering by the “Enabled” flag for a given Network Adapter slot. Note that the slots are 0-indexed, meaning the first NIC is referred to as Network Adapter #0.

When launching a node that supports multiple networks, simply assign multiple networks to the instance when you are launching it. The networks will be mounted on NICs in the same order that the networks are assigned; that is, the first assigned network will be mounted on Network Adapter #0, and the second on Network Adapter #1, and so on.

Floating IP Addresses

Instances on Chameleon are assigned a fixed IP address that can be used for local connectivity as well as NAT access to the public Internet. A publicly accessible IPv4 address (Floating IP address) is required in order to access Chameleon instances from the Internet or host public services. CHI@TACC and CHI@UC each have a limited number of public IP addresses that can be allocated to your instances.

The Getting started guide shows how to allocate Floating IP address to your nodes.


The Chameleon floating IP address pool is a shared and finite resource. Please be responsible and release any unused floating IP address, so other Chameleon users and projects can use them!

Floating DNS Records

Each Floating IP is also contained within a dedicated DNS A record; this means that you can access your instance over the Internet either via its Floating IP or a special hostname. This can be particularly helpful if you want to set up a TLS certificate for HTTPS to secure a service you are exposing over the web, e.g., with LetsEncrypt.


Hostname pattern (for IP AA.BB.CC.DD)




When your instance has a Floating IP address assigned, it is reachable directly over the public Internet. For this reason, it is important to consider the security of any services running on your instance. In particular, ensure that you have not allowed SSH authentication with passwords (this is disabled by default on Chameleon-supported images.)

In order to better protect Chameleon instances, Chameleon Ubuntu and CentOS base images come with baked-in firewall rules which severely restrict connections over the public internet. If using a different image or if you disable firewall rules, realize that any network services can potentially be exposed to the public Internet if your instance has a Floating IP attached.


Some commodity systems such as Apache Spark and Hadoop have in the past shipped with very insecure default settings. Pay particular attention to the security needs of your experiment when selecting what systems you need to install on your node, particularly when exposing the node to the Internet.


We’re here to help! If you want advice on how to securely run your experiment, feel free to file a Help Desk ticket.


Chameleon-supported Ubuntu and CentOS images are preconfigured with a firewall utility called firewalld enabled and the following rules set:

# sudo firewall-cmd --zone=public --list-services
dhcpv6-client ssh

These rules allow ssh traffic on port 22 over the public internet.


By default, all firewall changes are temporary, and will be lost on instance reboot. This is a saftey mechanism to avoid locking yourself out. To make changes permanent, execute:

sudo firewall-cmd --runtime-to-permanent
sudo firewall-cmd --reload

To enable HTTP/HTTPS on port 80 and 443:

sudo firewall-cmd --zone=public --add-service http
sudo firewall-cmd --zone=public --add-service https

Firewalld has many “built-in” rules for common services, but you can also enable communication over a specifc port using the command:

# list all open ports
sudo firewall-cmd --zone=public --list-ports

# open a new port
sudo firewall-cmd --zone=public --add-port=<port>/<protocol>

# example
sudo firewall-cmd --zone=public --add-port=9001/tcp

You can also permit connections from a specific ip or network, such as a trusted endpoint, or within your own isolated networks on Chameleon.

sudo firewall-cmd --zone=trusted --add-source=<your_subnet_cidr/netmask>

To enable this by default for all private IP ranges, you can do the following, but please note that this can be insecure on shared or routed networks (sharednet1, sharedwan1 and similar).

sudo firewall-cmd --zone=trusted --add-source=
sudo firewall-cmd --zone=trusted --add-source=
sudo firewall-cmd --zone=trusted --add-source=

Any other incomming connections will be denied.

For more examples and information, please see:

Security Groups

KVM@TACC supports Security Groups, which can be assigned directly to instances upon launch or after the instance is already running. By default, instances have no Security Groups applied, so all traffic is allowed.

Limit bound interfaces

Instead of binding a web service to all interfaces (e.g. for IPv4, :: for IPv6), consider listening only on the node’s private IP, which is not routable from the public Internet. If you can, listening on localhost ( is even safer. Most web services have a way to specify the bind address and some default to binding on all interfaces, which is often insecure.