Using CentOS but reporting here as the fix needs to go into the upstream source and then RHEL RPM anyway before going into CentOS, also reported there, see under "Additional info".

Description of problem:

cloud-init configures static network wrongly as:

IPADDR=10.0.88.151/8

instead of

IPADDR=10.0.88.151
PREFIX=8


Version-Release number of selected component (if applicable):

cloud-init-0.7.9-24.el7.centos.x86_64

How reproducible:

Always.


Steps to Reproduce:
1. Have a network configuration like (here via NoCloud source on Proxmox):

[root@centos1 ~]# mount | grep sr0
/dev/sr0 on /mnt/zeit type iso9660 (ro,relatime)
[root@centos1 ~]# cat /mnt/zeit/
meta-data       network-config  user-data       
[root@centos1 ~]# cat /mnt/zeit/network-config 
version: 1
config:
    - type: physical
      name: eth0
      mac_address: F2:15:C8:E1:0A:49
      subnets:
      - type: static
        address: 10.0.88.151/8
        gateway: 10.0.0.4
    - type: nameserver
      address:
      - 10.0.0.4
      search:
      - somedomain.de
 
2. Boot the image with this cloud init configuration


Actual results:

[root@centos1 network-scripts]# cat ifcfg-eth0.cloud-init.orig
# Created by cloud-init on instance boot automatically, do not edit.
#
BOOTPROTO=none
DEFROUTE=yes
DEVICE=eth0
GATEWAY=10.0.0.4
HWADDR=F2:15:C8:E1:0A:49
IPADDR=10.0.88.151/8
ONBOOT=yes
TYPE=Ethernet
USERCTL=no

Which leads to:

[root@centos1 ~]# LANG=C ifup eth0
ipcalc: both netmask and prefix specified
Usage: ipcalc [OPTION...]
  -c, --check Validate IP address for specified address family
  -4, --ipv4 IPv4 address family (default)
  -6, --ipv6 IPv6 address family
  -b, --broadcast Display calculated broadcast address
  -h, --hostname Show hostname determined via DNS
  -m, --netmask Display default netmask for IP (class A, B, or C)
  -n, --network Display network address
  -p, --prefix Display network prefix
  -s, --silent Don't ever display error messages

Help options:
  -?, --help Show this help message
  --usage Display brief usage message
ipcalc: both netmask and prefix specified
Usage: ipcalc [OPTION...]
  -c, --check Validate IP address for specified address family
  -4, --ipv4 IPv4 address family (default)
  -6, --ipv6 IPv6 address family
  -b, --broadcast Display calculated broadcast address
  -h, --hostname Show hostname determined via DNS
  -m, --netmask Display default netmask for IP (class A, B, or C)
  -n, --network Display network address
  -p, --prefix Display network prefix
  -s, --silent Don't ever display error messages

Help options:
  -?, --help Show this help message
  --usage Display brief usage message
ipcalc: both netmask and prefix specified
Usage: ipcalc [OPTION...]
  -c, --check Validate IP address for specified address family
  -4, --ipv4 IPv4 address family (default)
  -6, --ipv6 IPv6 address family
  -b, --broadcast Display calculated broadcast address
  -h, --hostname Show hostname determined via DNS
  -m, --netmask Display default netmask for IP (class A, B, or C)
  -n, --network Display network address
  -p, --prefix Display network prefix
  -s, --silent Don't ever display error messages

Help options:
  -?, --help Show this help message
  --usage Display brief usage message
arping: 10.0.88.151/8: Name or service not known
Error: any valid prefix is expected rather than "10.0.88.151/8/".
ERROR : [/etc/sysconfig/network-scripts/ifup-eth] Error adding address 10.0.88.151/8 for eth0.
arping: 10.0.88.151/8: Name or service not known
Error: any valid prefix is expected rather than "10.0.88.151/8/".
RTNETLINK answers: File exists


Expected results:

[root@centos1 network-scripts]# cat ifcfg-eth0
# Created by cloud-init on instance boot automatically, do not edit.
#
BOOTPROTO=none
DEFROUTE=yes
DEVICE=eth0
GATEWAY=10.0.0.4
HWADDR=F2:15:C8:E1:0A:49
IPADDR=10.0.88.151
PREFIX=8
ONBOOT=yes
TYPE=Ethernet
USERCTL=no


Additional info:

Upstream bug report:

network configuration fails on CentOS 7.5: using dhcp instead of static address
https://bugs.launchpad.net/cloud-init/+bug/1771116


I believe the offending code to be in "_write_network" in /usr/lib/python2.7/site-packages/cloudinit/distros/rhel.p