Description of problem:
The IP ranges of the introspection network and the br-ctlplane network in the example undercloud.conf file are:

dhcp_start = 192.0.2.5
dhcp_end = 192.0.2.100
inspection_iprange = 192.0.2.101,192.0.2.200

But the actual defaults once deployed are IP ranges with only 20 addresses available.

Version-Release number of selected component (if applicable):
instack-undercloud-5.1.0-4.el7ost.noarch

How reproducible:
100%

Steps to Reproduce:
1. Install an undercloud with the the IP ranges commented out in the undercloud.conf file

Actual results:
The 2 networks have only 20 available addresses, unlike the values shown in the undercloud.conf

Expected results:
The default values should be the same as the values that are commented out in undercloud.conf

Additional info: