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wilcdr's avatar
wilcdr
Icon for Nimbostratus rankNimbostratus
Oct 18, 2016

Making SNMP queries in iRules

From other questions people have asked, it looks like there is no built-in command for SNMP queries that you can make from iRules. Is that still true (running LTM 11.6)?   If that is not possible...
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  • Kai_Wilke's avatar
    Kai_Wilke
    Feb 08, 2023

    Running an periodic iCall Job in the Config-Plane to query SNMP and write results to a DG would be a much easier and elegant alternative. No? Dealing with ASN1-BER in iRules isn't much fun... 🙂

    Cheers, Kai

    LiefZimmerman : Good to see that the ordering in DevCentral has finally been changed, so that we can see if something gets added to rather old questions. Thanks!

wilcdr's avatar
wilcdr
Icon for Nimbostratus rankNimbostratus
Oct 19, 2016

Related question then. I think I got the packets formatted correctly and have connected a sideband connection using the 'connect' function, and then sent using the 'send' function. The returned number of bytes sent is 40 bytes. But then when I do the recv I don't get anything back.

 

My code looks like this:

 

   set conn_id [connect -protocol UDP -timeout 100 -status conn_status 192.168.0.1:161]
   set send_bytes [send -timeout 1000 -status send_status $conn_id $snmp_packet]
   set recv_bytes [recv -timeout 10000 -status recv_status $conn_id recv_packet]

conn_status comes back as "connected"

 

send_status comes back as "sent"

 

send_bytes comes back as 40

 

recv_status comes back as "received" or "closed" depending on how long I make the timeout

 

recv_bytes comes back as 0

 

I expect that even if my snmp_packet is not formatted correctly, it should still give me something back rather than 0 bytes.

 

Any idea what I'm doing wrong? There isn't any example or doc I can see for receiving UDP traffic from a sideband connection, so maybe there is something special I need to do for UDP connections? It feels like the connection is there, the request sent, but the response is coming back over a different port or something like that and the 'recv' command is not able to pick it up.