aha... maybe - just guessing now- there are some ACLs created on the cisco router, which disallow your IP or the network you're in to query the router. I mean: this seems logical if your script works on other hosts. have you tried the snmpwalk or snmpget command line tools? i always do this to check if the community string is correct and to see if i get any replies back...
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to ask a question is a moment of shame
to remain ignorant is a lifelong shame