Custom Alerts, Universal Device Pollers, Formulas and SNMP Tabular results

Question

We are using SNMP to pull the DHCP subnet status from our DHCP server. We pull free addresses and used addresses. Then we have a formula UnDP that calculates the percentage of available addresses in use. That all works fine. We can get tabular reports in the WebUI.

iso.org.dod.internet.private.enterprises.microsoft.software.dhcp.dhcpScope.scopeTable.scopeTableEntry

We want an alert when any subnet reaches a particular percentage threshold.

Our question, how do you work with tabular results in alerts? We are rockstars with variables in alerts; custom sql queries, the works. This one is killing us.

How does one set a trigger to use the rows of the table? How do I use the table as variables in the alert message?

ecklerwr1 · Answer

Seems like the trigger condition would have to have some ability to walk the table to check against it.  I've seen this implemented in ruby snmp lib not that it's going to help:

walk(object_list, index_column=0) {|index_vb| ...} Walks a list of ObjectId or VarBind objects using get_next until the response to the first OID in the list reaches the end of its MIB subtree.

The varbinds from each get_next are yielded to the given block as they are retrieved. The result is yielded as a VarBind when walking a single object or as a VarBindList when walking a list of objects.

Normally this method is used for walking tables by providing an ObjectId for each column of the table.

For example:

SNMP::Manager.open(:Host => "localhost") do |manager|    manager.walk("ifTable") { |vb| puts vb }  end  SNMP::Manager.open(:Host => "localhost") do |manager|    manager.walk(["ifIndex", "ifDescr"]) do |index, descr|      puts "#{index.value} #{descr.value}"    end  end

The index_column identifies the column that will provide the index for each row. This information is used to deal with "holes" in a table (when a row is missing a varbind for one column). A missing varbind is replaced with a varbind with the value NoSuchInstance.

Note: If you are getting back rows where all columns have a value of NoSuchInstance then your index column is probably missing one of the rows. Choose an index column that includes all indexes for the table.

axjww · Answer

IPAM noted.

We really want to understand this though because we have a lot of other resources that are tabular snmp.

smartd · Answer

Great question.  I've been trying to do the same thing with Juniper switch temperatures that are displayed in a table.  I couldn't find a way, but I'm still a newby

-=Dan=-