Security groups are sets of IP filter rules that are applied to all project instances, which define networking access to the instance. Group rules are project specific; project members can edit the default rules for their group and add new rule sets. All projects have a "default" security group which is applied to any instance that has no other defined security group. Unless you change the default, this security group denies all incoming traffic and allows only outgoing traffic to your instance. For information about updating rules using the dashboard, see . You can use the allow_same_net_traffic option in the /etc/nova/nova.conf file to globally control whether the rules apply to hosts which share a network. If set to: True (default), hosts on the same subnet are not filtered and are allowed to pass all types of traffic between them. On a flat network, this allows all instances from all projects unfiltered communication. With VLAN networking, this allows access between instances within the same project. You can also simulate this setting by configuring the default security group to allow all traffic from the subnet. False, security groups are enforced for all connections. Additionally, the number of maximum rules per security group is controlled by the security_group_rules and the number of allowed security groups per project is controlled by the security_groups quota (see ). From the command line you can get a list of security groups for the project, using the nova command: Ensure your system variables are set for the user and tenant for which you are checking security group rules for. For example: export OS_USERNAME=demo00 export OS_TENANT_NAME=tenant01 Output security groups, as follows: $ nova secgroup-list +---------+-------------+ | Name | Description | +---------+-------------+ | default | default | | open | all ports | +---------+-------------+ View the details of a group, as follows: $ nova secgroup-list-rules groupName For example: $ nova secgroup-list-rules open +-------------+-----------+---------+-----------+--------------+ | IP Protocol | From Port | To Port | IP Range | Source Group | +-------------+-----------+---------+-----------+--------------+ | icmp | -1 | 255 | 0.0.0.0/0 | | | tcp | 1 | 65535 | 0.0.0.0/0 | | | udp | 1 | 65535 | 0.0.0.0/0 | | +-------------+-----------+---------+-----------+--------------+ These rules are allow type rules as the default is deny. The first column is the IP protocol (one of icmp, tcp, or udp). The second and third columns specify the affected port range. The third column specifies the IP range in CIDR format. This example shows the full port range for all protocols allowed from all IPs. When adding a new security group, you should pick a descriptive but brief name. This name shows up in brief descriptions of the instances that use it where the longer description field often does not. For example, seeing that an instance is using security group "http" is much easier to understand than "bobs_group" or "secgrp1". Ensure your system variables are set for the user and tenant for which you are checking security group rules for. Add the new security group, as follows: $ nova secgroup-create Group Name Description For example: $ nova secgroup-create global_http "Allows Web traffic anywhere on the Internet." +--------------------------------------+-------------+----------------------------------------------+ | Id | Name | Description | +--------------------------------------+-------------+----------------------------------------------+ | 1578a08c-5139-4f3e-9012-86bd9dd9f23b | global_http | Allows Web traffic anywhere on the Internet. | +--------------------------------------+-------------+----------------------------------------------+ Add a new group rule, as follows: $ nova secgroup-add-rule secGroupName ip-protocol from-port to-port CIDR The arguments are positional, and the "from-port" and "to-port" arguments specify the local port range connections are allowed to access, not the source and destination ports of the connection. For example: $ nova secgroup-add-rule global_http tcp 80 80 0.0.0.0/0 +-------------+-----------+---------+-----------+--------------+ | IP Protocol | From Port | To Port | IP Range | Source Group | +-------------+-----------+---------+-----------+--------------+ | tcp | 80 | 80 | 0.0.0.0/0 | | +-------------+-----------+---------+-----------+--------------+ You can create complex rule sets by creating additional rules. For example, if you want to pass both http and https traffic, run: $ nova secgroup-add-rule global_http tcp 443 443 0.0.0.0/0 +-------------+-----------+---------+-----------+--------------+ | IP Protocol | From Port | To Port | IP Range | Source Group | +-------------+-----------+---------+-----------+--------------+ | tcp | 443 | 443 | 0.0.0.0/0 | | +-------------+-----------+---------+-----------+--------------+ Despite only outputting the newly added rule, this operation is additive (both rules are created and enforced). View all rules for the new security group, as follows: $ nova secgroup-list-rules global_http +-------------+-----------+---------+-----------+--------------+ | IP Protocol | From Port | To Port | IP Range | Source Group | +-------------+-----------+---------+-----------+--------------+ | tcp | 80 | 80 | 0.0.0.0/0 | | | tcp | 443 | 443 | 0.0.0.0/0 | | +-------------+-----------+---------+-----------+--------------+ Ensure your system variables are set for the user and tenant for which you are deleting a security group for. Delete the new security group, as follows: $ nova secgroup-delete GroupName For example: $ nova secgroup-delete global_http Source Groups are a special, dynamic way of defining the CIDR of allowed sources. The user specifies a Source Group (Security Group name), and all the users' other Instances using the specified Source Group are selected dynamically. This alleviates the need for individual rules to allow each new member of the cluster. Make sure to set the system variables for the user and tenant for which you are deleting a security group for. Add a source group, as follows: $ nova secgroup-add-group-rule secGroupName source-group ip-protocol from-port to-port For example: $ nova secgroup-add-group-rule cluster global_http tcp 22 22 The cluster rule allows ssh access from any other instance that uses the global_http group.