FAQ:Applications 04

Why can't I see values in the <INSERT ENTERPRISE HERE> tree?

Having said that there are two main reasons for not getting a response, the most likely cause of this problem is actually something else again.

The 'snmpwalk' command takes a point in the overall MIB tree, and tries to display all the values that lie within this subtree. However, it actually does this by issuing a series of "getnext" requests, until the variable returned lies outside the subtree of interest. If the very first request returns such an undesired value, then the command will terminate, without having displayed anything at all.

If an expicit starting point is given to 'snmpwalk', then it is reasonably clear what is happening, and that there is simply nothing in the subtree specified. However, if 'snmpwalk' is called without giving an explicit starting point, then it will display the contents of the 'mib-2' subtree. It will not attempt to traverse any 'private.enterprise' subtree, such as the UCD-specific objects (including any local extensions).

To walk the whole tree, specify a starting point of '.iso'. To walk a specific enterprise subtree, specify the root of this as the starting point - e.g:

       snmpwalk -v1 -c public localhost ucdavis

Or, of course, you can walk a selected portion of an enterprise subtree by specifying the appropriate starting point - e.g:

       snmpwalk -v1 -c public localhost ucdavis.version

If you still can't see any information, keep reading. The next few questions will probably help you.

   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?