How to troubleshoot active discovery?

[tenox]

I have a network with around 100 /24 subnets. NetXMS is not performing active discovery on some of them. Most work fine, but there are some subnets where NetXMS just won't go.

Yes, there is a firewall in between, but NetXMS host is allowed all to everywhere. I can ping hosts in the affected subnets manually from the NetXMS host OS, but NetXMS service is never sending anything there.

I have checked firewall logs, zero traffic, I have installed Wireshark, zero traffic - except when I ping manually.

I have enabled  -D 6 for netxmsd.exe. Reading the logs, there is nothing on the affected subnets.

NetXMS wont even try to go there.

Would it be possible that NetXMS doesn't have enough time to perform active discovery between the Window? I have set it to the default period. Active discovery is working fine for other networks.

My active discovery targets are:

192.168.0.0/255.255.0.0
10.0.0.0/255.0.0.0

For troubleshooting I have removed these and added the affected subnets alone:

192.168.1.0/255.255.255.0
10.1.10.0/255.255.255.0

Even with this these subnets only show devices (routers) that are found through other subnets, but not individual hosts, which I can ping from NetXMS host no problem.

(NetXMS 1.2.17 on Windows 2012 R2 x64)

Thanks,
Antoni

[tenox]

I did something else.

I removed all active discovery target, added just one single affected subnet, restarted NetXMS and now I see my sniffer is showing pings going to the subnet.

So it looks like active discovery freezes somehow and never gets to my subnets. How can I diagnose where any why?

Thanks,
Antoni