Trigger for an item that does not exist every time

[Lucas_G.]

Hi,

I run Zabbix 1.8.3 and I want to check for example if ssh is active (and generate an alert if not) on my HP Procurve switch.

so for ssh, I created an item whose OID is TCP-MIB::tcpConnState.0.0.0.0.22.0.0.0.0.0 (.1.3.6.1.2.1.6.13.1.1.0.0.0.0.22.0.0.0.0.0).

My problem is :

If ssh is disabled, this OID does not exist so my item generates an error and I can't create a trigger on it :

[B]snmpget -c public -Cf -v 2c <myswitchip> .1.3.6.1.2.1.6.13.1.1.0.0.0.0.22.0.0.0.0.0[/B]
TCP-MIB::tcpConnState.0.0.0.0.22.0.0.0.0.0 = No Such Instance currently exists at this OID

zabbix_server.log

6889:20100915:144348.508 Item [MySwitch:tcpConnState.0.0.0.0.22.0.0.0.0.0] error: OID [.1.3.6.1.2.1.6.13.1.1.0.0.0.0.22.0.0.0.0.0] value has unknown type [0x81]
  6889:20100915:144348.508 Parameter [MySwitch:tcpConnState.0.0.0.0.22.0.0.0.0.0] is not supported, old status [0]

My questions are :

- Do you know a way to create a trigger that generates an event if ssh is disabled, so if TCP-MIB::tcpConnState.0.0.0.0.22.0.0.0.0.0 returns : No Such Instance currently exists at this OID?

- If not, is there a way to check the tcp ports in listen state with zabbix with a snmptable technique? I mean, having Information triggers that show me which tcp ports are activated on my switch :

[B]snmptable <myswitchip> -c public -v 2c .1.3.6.1.2.1.6.13[/B]
SNMP table: TCP-MIB::tcpConnTable

 tcpConnState tcpConnLocalAddress tcpConnLocalPort tcpConnRemAddress tcpConnRemPort
       listen             0.0.0.0               23           0.0.0.0              0
       listen             0.0.0.0               80           0.0.0.0              0
       listen             0.0.0.0             1506           0.0.0.0              0
       listen             0.0.0.0             1513           0.0.0.0              0

Thanks.