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List: net-snmp-users
Subject: Re: Query: SNMP Prococol
From: Queenie de Melo <queenie245 () gmail ! com>
Date: 2010-10-20 10:32:03
Message-ID: AANLkTik=6L1T+o=vz5boH6bLNA5EFQ5gZV0U84oCux6o () mail ! gmail ! com
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Thanks Dave, for a wonderful explanation
Another question struck my mind...
We know that, the SNMP agent(Server) listens on port 161 for SNMP GET/SET
requests from the SNMP Manager (Client). The SNMP Agent then sends back a
response (GET-RESPONSE) to the SNMP Manager. This will be received by the
SNMP Manager on which Port? is it on Port 161 only?
And during the GET-RESPONSE sent from SNMP Agent to SNMP Manager--- Who is
the Server and who is the Client??Does it get reversed or remains the
same(SNMP agent as Server and SNMP Manager as Client)
On Mon, Oct 18, 2010 at 5:52 PM, Dave Shield <D.T.Shield@liverpool.ac.uk>wrote:
> On 18 October 2010 12:57, Queenie de Melo <queenie245@gmail.com> wrote:
> > So the SNMP agent(Server) listens on port 161 for SNMP GET/SET requests
> > from the SNMP Manager (Client)
>
> Correct.
>
> (Strictly speaking, the agent can listen on any available port,
> but port 161 is the standard port for SNMP information retrieval)
>
>
>
> > What about in Case of traps?
> >
> > The SNMP Manager in this case listens on UDP port 162 for the Traps sent
> by
> > the SNMP Agent. So in this case, is it that the SNMP Manager is .... the
> > Server and SNMP Agent is the client??
>
> That's right.
>
> The SNMP agent (or some other application that generates traps) is the
> client
> and the application that receives the trap is the server.
> The official terminology is "notification generator" and
> "notification receiver".
>
> The notification receiver may be the same SNMP manager application as the
> one generating information retrieval requests. Or it may be a dedicated
> trap-receiving application (such as the Net-SNMP 'snmptrapd').
> But the most important thing here is that the client-server relationship
> is
> reversed for traps, when compared to GET/SET requests.
>
>
>
> > Another query i had is: what exactly are SNMP INFORMS?
>
> A trap is sent from the agent to the trap receiver, but there's no
> acknowledgement sent back. So the agent doesn't know whether
> the trap got there safely (let alone whether it was acted upon).
>
> An INFORM is essentially the same as a trap, except that it *does*
> trigger an acknowledgement. So the agent (or other notification
> generator application) knows that the inform was received.
> (Whether the receiver actually did anything with it is a different
> question!)
>
> Think of this as the same as "read receipt messages" in the context of
> email.
>
>
>
>
> >> SNMP inform is nothing it's an acknowledgment mechanisim in SNMP. which
> is
> >> getting supported from snmpv2c and snmpv3 onwards
> >
> > Is it sent from the Manager to the Agent in response to a TRAP?
>
> No
>
> >
> or is it
> > sent from Agent to Manager just like a trap (but u want manager to ack
> the
> > receiptof trap)
>
> Yes.
>
>
>
> > or is it sent from NMS(SNMP Manager) to another SNMP Manager
> > ????
>
> "SNMP Manager" is something of a vague term.
> Any SNMP application can act in various different roles - hence the
> current specifications talk in terms of "notification receiver" or
> "notification generator" (and similarly for GET/SET requests)
>
> It's perfectly possible for one SNMP manager application to signal
> to another, using traps or informs. But the most typical use of traps
> or informs would be from an agent to an NMS.
>
> Dave
>
[Attachment #5 (text/html)]
Thanks Dave, for a wonderful explanation<div><br></div><div>Another question struck \
my mind... </div><div><div class="im">We know that, the SNMP agent(Server) listens on \
port 161 for SNMP GET/SET requests from the SNMP Manager (Client). The SNMP Agent \
then sends back a response (GET-RESPONSE) to the SNMP Manager. This will be received \
by the SNMP Manager on which Port? is it on Port 161 only? </div> <div class="im">And \
during the GET-RESPONSE sent from SNMP Agent to SNMP Manager--- Who is the Server and \
who is the Client??Does it get reversed or remains the same(SNMP agent as Server and \
SNMP Manager as Client)</div></div> <div><br><br><div class="gmail_quote">On Mon, Oct \
18, 2010 at 5:52 PM, Dave Shield <span dir="ltr"><<a \
href="mailto:D.T.Shield@liverpool.ac.uk">D.T.Shield@liverpool.ac.uk</a>></span> \
wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px \
#ccc solid;padding-left:1ex;"> <div class="im">On 18 October 2010 12:57, Queenie de \
Melo <<a href="mailto:queenie245@gmail.com">queenie245@gmail.com</a>> \
wrote:<br> > So the SNMP agent(Server) listens on port 161 for SNMP GET/SET \
requests<br> > from the SNMP Manager (Client)<br>
<br>
</div>Correct.<br>
<br>
(Strictly speaking, the agent can listen on any available port,<br>
but port 161 is the standard port for SNMP information retrieval)<br>
<div class="im"><br>
<br>
<br>
> What about in Case of traps?<br>
><br>
> The SNMP Manager in this case listens on UDP port 162 for the Traps sent by<br>
</div>> the SNMP Agent. So in this case, is it that the SNMP Manager is .... \
the<br> <div class="im">> Server and SNMP Agent is the client??<br>
<br>
</div>That's right.<br>
<br>
The SNMP agent (or some other application that generates traps) is the client<br>
and the application that receives the trap is the server.<br>
The official terminology is "notification generator" and<br>
"notification receiver".<br>
<br>
The notification receiver may be the same SNMP manager application as the<br>
one generating information retrieval requests. Or it may be a dedicated<br>
trap-receiving application (such as the Net-SNMP 'snmptrapd').<br>
But the most important thing here is that the client-server relationship is<br>
reversed for traps, when compared to GET/SET requests.<br>
<div class="im"><br>
<br>
<br>
> Another query i had is: what exactly are SNMP INFORMS?<br>
<br>
</div>A trap is sent from the agent to the trap receiver, but there's no<br>
acknowledgement sent back. So the agent doesn't know whether<br>
the trap got there safely (let alone whether it was acted upon).<br>
<br>
An INFORM is essentially the same as a trap, except that it *does*<br>
trigger an acknowledgement. So the agent (or other notification<br>
generator application) knows that the inform was received.<br>
(Whether the receiver actually did anything with it is a different question!)<br>
<br>
Think of this as the same as "read receipt messages" in the context of \
email.<br> <div class="im"><br>
<br>
<br>
<br>
>> SNMP inform is nothing it's an acknowledgment mechanisim in SNMP. which \
is<br> >> getting supported from snmpv2c and snmpv3 onwards<br>
><br>
> Is it sent from the Manager to the Agent in response to a TRAP?<br>
<br>
</div>No<br>
<div class="im"><br>
> or is \
it<br> > sent from Agent to Manager just like a trap (but u want manager to ack \
the<br> > receiptof trap)<br>
<br>
</div>Yes.<br>
<div class="im"><br>
<br>
<br>
> or is it sent from NMS(SNMP Manager) to another SNMP Manager<br>
> ????<br>
<br>
</div>"SNMP Manager" is something of a vague term.<br>
Any SNMP application can act in various different roles - hence the<br>
current specifications talk in terms of "notification receiver" or<br>
"notification generator" (and similarly for GET/SET requests)<br>
<br>
It's perfectly possible for one SNMP manager application to signal<br>
to another, using traps or informs. But the most typical use of traps<br>
or informs would be from an agent to an NMS.<br>
<font color="#888888"><br>
Dave<br>
</font></blockquote></div><br></div>
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