Unable to obtain a certificate using fastcert

[nnnzzznnn]

First of all, I would like to thank you for your quick response.
City of Brooklyn.
I'm trying to use fastcert to obtain certificate to upload it to Motorolla SB5101.
but I'm unable to do so because I'm always getting no cert available when I run fastcert program.
I'm not sure what I'm missing.
I don't know the range to use.
I put the following:
Community String (public) - Thread (800) Retries (2) - Timeout (2) - the port 161 and 162 - the range 10.41.0.0 to 10.41.255.255.
How to find the right range????
Thanks agian.

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