#266 netdisco subnet utiiization report

[Vladimir Puchkov]

Hi. I have a problem when request subnet utilization report with many subnet. This change fix this problem for me

diff --git a/Netdisco/lib/App/Netdisco/DB/Result/Virtual/SubnetUtilization.pm b/Netdisco/lib/App/Netdisco/DB/Result/Virtual/SubnetUtilization.pm
index 1ce4d9d..e3b6778 100644
--- a/Netdisco/lib/App/Netdisco/DB/Result/Virtual/SubnetUtilization.pm
+++ b/Netdisco/lib/App/Netdisco/DB/Result/Virtual/SubnetUtilization.pm
@@ -14,7 +14,7 @@ PACKAGE->result_source_instance->view_definition(<<'ENDSQL');
SELECT net as subnet,
power(2, (32 - masklen(net))) as subnet_size,
count(DISTINCT ip) as active,
- round(100 * count(DISTINCT ip) / (power(2, (32 - masklen(net))) - 2)) as percent
+ round(100 * count(DISTINCT ip) / (power(2, (32 - masklen(net))))) as percent
FROM (
SELECT DISTINCT net, ni.ip
FROM subnets s1, node_ip ni

May be, this way is wrong. Can you explain is my fix is correct?
Thank you.

[Oliver Gorwits]

Hello, yes, thanks for this bug report and patch!!

What is happening is that if you have a /31 prefix on your network then the maths causes a divide-by-zero error. Your fix removes this error.

More info on /31:
http://packetlife.net/blog/2008/jun/18/using-31-bit-subnets-on-point-point-links/

I have applied the fix for the next release.