Re: SNMP v3 Proxy to SNMP v1 host

After doing some more research, I think the question I was really asking was
"How can I set the SNMPv3 context?" (specifically, the agent) which happens
to be answered here:

http://www.net-snmp.org/wiki/index.php/How_can_I_set_the_SNMPv3_context

You were 100% correct about your suggestion. I couldn't find an OID that was
implemented only on host3 (you said host2 but I think you meant host3) that
wasn't on host2. So what I did was issue a v3 snmpwalk against host2 from
host1 for the module "ip" and I received host2's IP info. I then disabled
this module in the snmpd.options file with the -I flag on host2 (side note -
to disable either one module or a list of modules, you have to prefix the
module name with '-'. If you don't use that, the documentation says that
will be the only module loaded. Interestingly enough, when I first did that
[left out the "-" prefix], my snmpv3 user was deleted from
/var/net-snmp/snmpd.conf [bug?]) and ran the snmpwalk against host2 module
"ip" and the data that was returned was for host3. A tcpdump confirmed that
host2 was proxying the data to host3.

So... to sum this up, this does in a way solve my problem, which is, how do
I send an snmp request from host1 using snmpv3 to host2 and have host2 proxy
the request to host3 using snmpv1/2c, without having to supply the context
in host1's snmp request. This could potentially work for me if I disable all
modules on host2, not sure if that's even possible. However, what I didn't
mention before was that I need host2 to proxy more then just host3, but
host4, host5, host6, etc. I don't see this work around working in this
scenario.

If only all of my client software had the "context" implemented it their
snmp requests. Anyway, thanks for the assistance on this.



On Sun, Jan 16, 2011 at 2:29 PM, Dave Shield <[email protected]>wrote:

> On 16 January 2011 17:37, Jacob Seeley <[email protected]> wrote:
> >                                                  I need to be able to
> send an
> > SNMPv3 request to host2 without context and have host2 map
> > that request so that it's proxied to host3
>
>
> > How can I accomplish this without having to use context in my client's
> SNMP
> > request? Is VACM the answer?
>
> No, I don't believe so.
>
> The basic problem is that when the agent received the (default context)
> request, it has two possible sources for this information - the proxy
> connection to host3, and the local MIB modules that it handles itself.
>    The design of the Net-SNMP agent is that it always chooses the
> "more focused" registration, which will invariably be the local module.
>
> Try issuing a query for an OID that is *only* implemented on host2,
> and see if that works.
> You might also try disabling some of the local MIB modules
> (using -I-{module}) and see if that helps.
>
> Dave
>

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