Networks

3. Networks#

BlueBanquise networking relies on the networks dict definition in the Ansible inventory, and on nodes network_interfaces definitions.

3.1. Understanding logic#

Before listing available parameters, it is important to understand the network logic.

Under networks key: each network listed that starts with previx net- is considered a management network (also refered as an administration network), while other networks are considered basic networks. A management network is designed to host low level vital resources, like DHCP, DNS, NTP, PXE, BMCs management (IPMI/RedFish), etc, while basic networks are designed to host all other usages, like data transfers, calculations exchanges, etc.

Under network_interfaces of a node:

  1. First interface in the list is considered by the stack the “ping” (node_main_resolution) interface, and so resolving direct node hostname will end up on this interface

  2. First interface in the list, linked to a management network, is considered by the stack being the node deployment interface (node_main_network), and so is used by PXE and Ansible (ssh) to deploy and reach the node.

If you need, you can check the logic code (Jinja2) in the vars plugin of bluebanquise infrastructure collection.

3.2. Networks definition#

Networks are defined under networks dict key. While in normal time in group_vars/all/networks.yml file, the networks definition can be defined at multiple places in the inventory (groups, hosts, etc.) to allow sophisticated configurations. For example, if networks configuration must be different on node login1 than on the other nodes, it is possible to create folder host_vars/login1/, and redefine networks here, so that login1 will inherit this configuration instead of the global one.

Note that while IPv4 is supported everywhere, IPv6 is only experimentaly supported by most roles of the stack. If you need full IPv6 support, please open a Feature request on github.

3.2.1. Mandatory keys#

The bare minimal to define a network is the following:

networks:
  net-admin:
    subnet: 10.10.0.0
    prefix: 16

subnet and prefix keys are mandatory.

3.2.2. Gateway and routes#

It is possible to define a gateway or custom routes for a network.

To define a gateway, use gateway4 (gateway4 replaces gateway which is now deprecated):

networks:
  net-admin:
    subnet: 10.10.0.0
    prefix: 16
    gateway4: 10.10.2.1

If you need to define routes, it is possible to use the routes4 list to define your routes. Format then is the following: <subnet/prefix> <gateway> <metric>, metric being optional.

networks:
  net-admin:
    subnet: 10.10.0.0
    prefix: 16
    routes4:
      - 10.11.0.0/24 10.10.0.2
      - 10.12.0.0/24 10.10.0.2 300

3.2.3. MTU#

It is possible to define an MTU for a whole network, using the mtu key:

networks:
  net-admin:
    subnet: 10.10.0.0
    prefix: 16
    mtu: 9000
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