Re: [pysnmp-users] Unknown SNMP engine ID encountered - but only on one device
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From: Whitesell, K. <Ken...@ws...> - 2017-10-23 12:58:07
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Ok, Sunday afternoon brain cramp. Seems to me like each request is going to go out through a different source port, and so the responses will come back through that port. As long as a different port is used for sending the requests, the responses should be able to be segregated by port. Duh. Now I can start digging. Thanks again so much for your help. Ken -----Original Message----- From: Ilya Etingof [mailto:et...@gm...] Sent: Sunday, October 22, 2017 4:33 AM To: Whitesell, Ken <Ken...@ws...> Cc: pys...@li... Subject: Re: [pysnmp-users] Unknown SNMP engine ID encountered - but only on one device Hi Ken, It seems [1] that a well-behaving SNMPv3 agent is supposed to respond from the same interface it received request from. But that does not solve your problem, obviously. ;-) On the other hand, I have not found explicit prohibition of the mis-matching addresses situation in SNMPv3 / USM RFCs. So may be pysnmp should not be that strict? Would it help to send SNMP commands to that interface your device tends to respond from? Then may be request/response IPs would match from pysnmp’s perspective… If you are interested in resolving this issue at the pysnmp side, I may try looking into your pysnmp debug log to figure out where exactly the mismatch breaks things… 1. https://tools.ietf.org/html/rfc3412#section-4.2.2.1 > On 22 Oct 2017, at 08:40, Whitesell, Ken via pysnmp-users <pys...@li...> wrote: > > First, my sincere thanks for the replies to my question. I’ve learned a lot more about SNMP from a protocol perspective than I’ve ever needed to know in working with and around it for the past 10 years or so. > > So what I’m thinking so far is that I believe the root cause is an ip address problem. These devices are all on IPv6, and typically have multiple addresses assigned to each interface. What I’m seeing from tcpdump and wireshark is that the UDP packet being returned from the device shows a different source IP address than the address to which the request is being sent. > (In other words, I’m sending a request from 2600:800:280::a036 to the > device at 2600:800:280::4444. However, the packet being returned has > the MAC-related auto-generated address in the lower half – > 2600:800:280:0:226:adff:fe05:1111, where both those addresses are > assigned to the same interface.) > > Since this is a connectionless protocol, is it a reasonable assumption that since the response received isn’t coming from the same IP address to which the request was sent, that that might be the cause of the error? > > Thanks, > Ken > > ---------------------------------------------------------------------- > -------- Check out the vibrant tech community on one of the world's > most engaging tech sites, Slashdot.org! > http://sdm.link/slashdot______________________________________________ > _ > pysnmp-users mailing list > pys...@li... > https://lists.sourceforge.net/lists/listinfo/pysnmp-users |