Processing a GET-NEXT request

Parsing a GET-NEXT request yields two parameters: the object ID of the requested variable and the reason for this request. This allows the subagent to return the name, type, and value of the next supported variable, whose name lexicographically follows that of the passed object ID.

Subagents can support several different groups of the MIB tree. However, the subagent cannot jump from one group to another. You must determine the reason for the request to then determine the path to traverse in the MIB tree. The second parameter contains this reason and is the group prefix of the MIB tree that is supported by the subagent.

If the object ID of the next variable supported by the subagent does not match this group prefix, the subagent must return SNMP_NO_SUCH_NAME. If required, the SNMP agent calls on the subagent again and passes a different group prefix.

For example, if you have two subagents, the first subagent registers two group prefixes, A and C, and supports variables A.1, A.2, and C.1. The second subagent registers the group prefix B, and supports variable B.1.

When a remote management station begins dumping the MIB, starting from A, the following sequence of queries is performed:

Subagent 1 gets called:
 
get-next(A,A) == A.1
get-next(A.1,A) == A.2
get-next(A.2,A) == error(no such name)
 
Subagent 2 is then called:
 
get-next(A.2,B) == B.1
get-next(B.1,B) == error(no such name)
 
Subagent 1 is then called:
get-next(B.1,C) == C.1
get-next(C.1,C) == error(no such name)