static-routes

Purpose

Compute nodes sometimes need multiple NICs. Frequent management of routing tables over multiple nodes in a cluster might be a cumbersome process if not automated. This simple Ansible role will help this task, and will keep the single source ot truth (for routing tables) in inventory. Every time the routing need to be extended, a set of metadata attributes can be appended to the static routing table block. Those attributes are "name", "contact", "date" and "comment", followed by tbe routing entries. This way a sysadmin can keep track of ownership and purpose of routes.

This role does not have intention to be generic network management.

Prerequisites

1 The full definition of interface is in the file /etc/sysconfig/network-scripts/ifcfg-<interface-name>

[root@ip-172-201-1-10 network-scripts]# ll ifcfg-*
-rw-r--r--. 1 root root 193 Jul  6 19:03 ifcfg-eth0
-rw-r--r--. 1 root root 199 Jul  6 18:41 ifcfg-eth1
-rw-r--r--. 1 root root 254 May  3  2017 ifcfg-lo

2 The /etc/sysconfig/network-scripts/ifcfg-<interface-name> file contains entry: GATEWAY=<ip4-address>

BOOTPROTO=dhcp
DEVICE=eth0
HWADDR=02:47:bc:0d:1d:9a
ONBOOT=yes
TYPE=Ethernet
USERCTL=no
DEFROUTE=yes
GATEWAY=172.201.1.1

Please note that GATEWAY parameter might not be configured OOTB, or by default.

Example

Inventory and hosts file

Ansible inventory inventories/<inventory>/all/static-routes-<interface-name> contains definition of desired routing. There could be multiple entries on the list of static_routes_eth0 names.

network_configuration_path: "/etc/sysconfig/network-scripts"
static_routes_eth0:
  - name: External routing example
    contact: [email protected]
    date: 2019.07.03
    comment: Example for eth0
    routes:
      - 172.15.1.2
      - 10.1.1.1
      - 10.2.2.2

Hosts file ...

[all]
ip-172-201-1-10 ansible_ssh_host=ip-172-201-1-10.eu-central-1.compute.internal ansible_ssh_user=ansible

[public-hosts]
ip-172-201-1-10

Playbook

- hosts: public-hosts
  become: yes
  become_method: sudo
  become_user: root
  roles:
    - static-routes

The Ansible playbook could be run as: $ ansible-playbook static-routes.yml --ask-become-pass

Result

Running the role will create new routes in the /etc/sysconfig/network-scripts/route-<interface-eth0 file as defined in the inventory:

# Project: External routing
# Contact: [email protected]
# Change: 2019.07.03
# Comment: Example for eth0 nic
172.15.1.2 via 172.201.1.1
10.1.1.1 via 172.201.1.1
10.2.2.2 via 172.201.1.1

And it will also restart network and set the routing for the node to:

[root@ip-172-201-1-10 ~]# netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         172.201.1.1     0.0.0.0         UG        0 0          0 eth0
0.0.0.0         172.201.2.1     0.0.0.0         UG        0 0          0 eth1
10.1.1.1        172.201.1.1     255.255.255.255 UGH       0 0          0 eth0
10.2.2.2        172.201.1.1     255.255.255.255 UGH       0 0          0 eth0
172.15.1.2      172.201.1.1     255.255.255.255 UGH       0 0          0 eth0
172.201.1.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0
172.201.2.0     0.0.0.0         255.255.255.0   U         0 0          0 eth1
[root@ip-172-201-1-10 network-scripts]#