[AGENT++] SNMP++v3.2.10a: Callback data, pdu_error and some protocol specifics questions ...

[Arunas Mazeika]

            Hello, I would like to understand some things that are
bodering me. The first one is, what is the purpose of the callback data
when I register to traps?. I saw that in the Qt example they placed
"this" in the member function notify_register. I really don't understand
it. I would be nice if somebody can explain it to me. The second one is,
how does SNMP++ knows when an incoming PDU has errors, what kind of
check is performed?. The last one is regarding to the protocol itself.
When I use the function broadcast_discovery with the network base
address, I get funny results. I am connected directly to a switch (port
192.168.1.2); the switch is connected to a router (port 192.168.1.3).
When I use the base address 192.168.1.0), both responded with their
Gateways (192.168.1.2 and 192.168.1.3). Then I tried to do the something
but in another segment. Same topology, but in another segment, that is,
some hosts connected to a switch which is connected to a router. When I
used the network base address for discovery in that segment, the router
responded this time with two Gateways. The first one is the port where
that network is connected and the second one is the port where the PDU
entered to the router. The router has other gateways that are not show
in the response, so it only shows the one where the PDU entered. The
switch didn't respond this time. I figured out that the
broadcast_discovery is a get to the sysdescr object that allows
multiples responses, in order to catch all the agents when the broadcast
address is used. What I think is that this should be some kind of
specific issue with the equipments (routers switches), because they are
assuming that the network base address is their address too. What I
don't get is why in the first case is different than the second one. I
mean why the switch responded in the first case and in the second it
didn't, and why the router's gateway where the PDU entered is shown in
the second case. Well this is it, thanks in advance.
 
Arunas Mazeika