FAQ:Applications 12

Why can't I set any variables in the MIB?

There are three possible reasons for this:

• Many MIB objects are defined as "read-only" and inherently cannot be changed via SET requests. Attempts to do so will typically be rejected by the 'snmpset' command without ever being sent to the agent.

• Of those objects that can in principle be changed, the agent may not include the code necessary to support SET requests. (GET and GETNEXT are much easier to handle - particularly for objects relating to the internals of the underlying operating system).

• Even if SET support has been implemented, the agent may not be configured to allow write access to this object.

Ready-installed distributions (such as those shipped with Linux) tend to be configured with read-only access to part of the mib tree (typically just the system group) and no write access at all.

To change this, you will need to set up the agent's access control configuration. See the AGENT section for more details.

Note that neither the community string "public" nor "private" can be used to set variables in a typical default configuration.

   FAQ:Applications
   

1. How do I add a MIB?
2. How do I add a MIB to the tools?
3. Why can't I see anything from the agent?
4. Why doesn't the agent respond?
5. I can see the system group, but nothing else. Why?
6. Why can't I see values in the <ENTERPRISE> tree?
7. The agent worked for a while, then stopped responding. Why?
8. Requesting an object fails with "Unknown Object Identifier" Why?
9. Why do I get "noSuchName" when asking for "sysUpTime" (or similar)?
10. Why do I sometimes get "End of MIB" when walking a tree, and sometimes not?
11. How do I use SNMPv3?
12. Why can't I set any variables in the MIB?
13. Variables seem to disappear when I try to set them. Why?
14. Why can't I change sysLocation (or sysContact)?
15. I get an error when trying to set a negative value - why?
16. I get an error when trying to query a string-indexed table value - why?
17. How should I specify string-index table values?
18. How do I send traps and notifications?
19. How do I receive traps and notifications?
20. How do I receive SNNMPv1 traps?
21. Why don't I receive incoming traps?
22. My traphandler script doesn't work when run like this - why not?
23. How can the agent receive traps and notifications?
24. How big can an SNMP request (or reply) be?
25. How can I monitor my systems (disk, memory, etc)?
26. Applications complain about entries in your example 'snmp.conf' file. Why?
27. OK, what should I put in snmp.conf?
28. How do I specify IPv6 addresses in tools command line arguments?