FAQ:Agent 04 & 05

How do I add functionality?

Adding a MIB essentially involves writing some code to implement the objects defined in the new MIB. There are three basic approaches that can be used to do this:

• The agent can invoke an external command or shell script to return the necessary information. There are several possible variations on this approach - see the next entry for details.

• The agent can pass the request off to another (sub-)agent, which already implements the required MIB. Again, there are several ways of doing this - including AgentX, SMUX and proxied SNMP. See the next entry but one for details.

• You can write code to implement the new MIB objects, and include this within the agent. This is most commonly C (or C++) code, although the agent can also support MIB modules implemented in perl.
  See the next section (CODING) for more details.

Note that there is no visible difference between external commands, subagents, and modules implemented within the main agent itself. Tools querying the agent will see a single MIB structure.

   FAQ:Agent
   

1. What MIBs are supported?
2. What protocols are supported?
3. How do I configure the agent?
4. How do I remove a MIB from the agent?
5. I've installed a new MIB file. Why can't I query it?
6. How do I add a MIB to the agent?
7. What's the difference between 'exec', 'sh', 'extend' and 'pass'?
8. What's the difference between AgentX, SMUX and proxied SNMP?
9. What is the purpose of 'dlmod'?
10. Which extension mechanism should I use?
11. Can I use AgentX when running under Windows?
12. How can I run AgentX with a different socket address?
13. How can I turn off SMUX support?
14. How can I combine two copies of the 'mib2' tree from separate subagents?
15. What traps are sent by the agent?
16. Where are these traps sent to?
17. How can I send a particular trap to selected destinations?
18. When I run the agent it runs and then quits without staying around. Why?
19. After a while the agent stops responding, and starts eating CPU time. Why?
20. How can I stop other people getting at my agent?
21. How can I listen on just one particular interface?
22. The agent is complaining about 'snmpd.conf'. Where is this?
23. Why does the agent complain about 'no access control information'?
24. How do I configure access control?
25. How do I configure SNMPv3 users?
26. The 'createUser' line disappears when I start the agent. Why?
27. What's the difference between /var/net-snmp and /usr/local/share/snmp?
28. My new agent is ignoring the old snmpd.conf file. Why?
29. Where should the snmpd.conf file go?
30. Why am I getting "Connection refused"?
31. Why can't I see values in the UCDavis 'extensible' or 'disk' trees?
32. Why can't I see values in the UCDavis 'memory' or 'vmstat' tree?
33. What do the CPU statistics mean - is this the load average?
34. How do I get percentage CPU utilization using ssCpuRawIdle?
35. What about multi-processor systems?
36. The speed/type of my network interfaces is wrong - how can I fix it?
37. The interface statistics for my subinterfaces are all zero - why?
38. Does the agent support the RMON-MIB?
39. What does "klread: bad address" mean?
40. What does "nlist err: wombat not found" (or similar) mean?
41. What does "Can't open /dev/kmem" mean?
42. The system uptime (sysUpTime) returned is wrong!
43. Can the agent run multi-threaded?
44. Can I use AgentX (or an embedded SNMP agent) in a threaded application?