Re: no response from devices when querying multiple oids

On Tue, Nov 19, 2013 at 6:38 AM, Aleksandrs Saveljevs <
[email protected]> wrote:

> I have played a bit more and the conjecture turned out to be (at least
> partially) false.
>
> The way I played was attempt to query string objects with long values:
>
> $ snmpget -v 2c -c public 192.168.1.1 IF-MIB::ifAlias.3
> IF-MIB::ifAlias.3 = STRING: Builtin r8139/8129 - Realtek RTL8139 Fast
> Ethernet  Bus 0 Slot
>
> $ { for i in {1..13}; do echo 'IF-MIB::ifAlias.3'; done } | xargs
> snmpget -d -r 0 -v 2c -c public 192.168.1.1
>
> Sending 254 bytes to UDP: [192.168.1.1]:161->[0.0.0.0]:0
> ...
>
> Timeout: No Response from 192.168.1.1.
>
> So the device sends no response to a 254-byte request. If 12 copies are
> queried, then it works OK by responding with a 1020-byte packet.
>

I can't comment on your specific scenario, but I _do_ know that there
is a design limit in the strings accepted into snmpd via its AgentX
interface, and anything longer will be (semi-silently) dropped.
Perhaps the same implementation restriction also applies to strings
coming from other areas within snmpd.

Because although the spec for OCTET STRINGS allows for 2^16
in length, there are also other words (and warnings) that say
'there can be other implementation-specific limitations'.

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