Discovery plugin not detecting devices on certain subnets

[Ed_Howard]

Alright this is a strange one.

I have several subnets in my environment. I have set the Discovery plugin to scan these subnets and automatically add and graph the devices it finds. On the majority of these subnets the discovery tool is working as expected. However on certain subnets it cannot find any devices. All devices are of the same type (Motorola Canopy radios), running the same SNMP string and version. An example of the problem I am having would be as follows:

Scanned subnet 10.100.90.* found and added 100 plus devices
Scanned subnet 10.100.100.* did not find any devices.

I can however manually add and graph the devices on the 10.100.100.* subnet.

This seems a little strange to me and is driving me nuts. One other little annoyance is that there seems to be a character amount limitation on the Console->Cacti Settings->Misc page as to subnets that are to be scanned.

The log is not returning any errors only or anything unusual, any help would be appreciated.

Date Wed, 19 Jan 2011 14:21:06 -0800
Cacti Version 0.8.7g
Cacti OS unix
SNMP Version NET-SNMP version: 5.1.2
RRDTool Version RRDTool 1.2.x
Hosts 580
Graphs 614
Data Sources Script/Command: 6
SNMP Query: 608
Script - Script Server (PHP): 1
Total: 615
Poller Information
Interval 60
Type spine
Items Action[0]: 1180
Action[1]: 6
Action[2]: 1
Total: 1187
Concurrent Processes 1
Max Threads 6
PHP Servers 1
Script Timeout 25
Max OID 10
Last Run Statistics Time:13.5505 Method:spine Processes:1 Threads:6 Hosts:581 HostsPerProcess:581 DataSources:1186 RRDsProcessed:591
PHP Information
PHP Version 5.1.6
PHP OS Linux
PHP uname Linux localhost.localdomain 2.6.9-89.33.1.plus.c4smp #1 SMP Thu Dec 2 12:09:37 EST 2010 i686
PHP SNMP Installed
max_execution_time 30
memory_limit 32M

[gandalf]

Did you verify, that e.g. no firewall blocks specific type of traffic that is used by the discovery plugin?
R.

[Ed_Howard]

Hi Gandalf,

Thanks for the help and the quick reply.

The vlans that I am having issues with are on the same switch and they all appear to be configured the same. Does the discovery tool use a separate protocol to detect these devices? If so could you tell me what that is and I will do some more trouble shooting on that end. It just seems strange that I can manually add the devices in Cacti but am unable to find them with the discovery tool. In fact it appears that the devices do not even reply to a ping attempt from the Cacti server. I really appreciate all the help and again please excuse my ignorance.

[gandalf]

In fact it appears that the devices do not even reply to a ping attempt from the Cacti server.

How did you test?
R.

[Ed_Howard]

Hi Gandalf,

I just sent you a PM as well if you would rather continue this off the discussion board I would understand.

I ran the command "ping 10.100.100.155" from the terminal using ssh to connect. The device replied. However when I look in the clog console I see that hardly any devices responded to ping and only 1 responded to the SNMP query and did not match the discovery template so was not added.

01/24/2011 02:18:22 PM - DISCOVER: Poller[0] 245 IPs Scanned, 9 IPs Responded to Ping, 0 Responded to SNMP, 0 Device Added, 0 Graphs Added to Cacti
01/24/2011 02:14:17 PM - POLLER: Poller[0] Network Discover is now running

The one device that responded to the ping was the cisco switch. The other anomolie is that the other 8 devices that did respond to the ping did not show up in the disocvery tab. There are several hundred devices on this one subnet that I am testing.

I hope this helps and if there is anything else you need please let me know.

[gandalf]

Ping is a beast. Opening an ICMP socket under php (at least as coded in cacti) requires specific privileges (aka: root). We do not recommend that. I always advertise using SNMP only wherever possible. You will need this for polling, so why not use it for discovery? But make sure to have all snmp communities listed in the discovery settings.
R.