[mrtg] Target error

[Andrea Bencini]

I installed mrtg
It is working.
My question is:
When I use the "Target" in numeric form I haven't problem
Target[server.cpuUser]: 
.1.3.6.1.4.1.2021.11.50.0&.1.3.6.1.4.1.2021.11.50.0:public at 10.100.0.1

When I use the "Target" in this form
Target[server.cpuUser]: 
.1.3.6.1.4.1.2021.11.ssCpuRawUser.0&.1.3.6.1.4.1.2021.11.ssCpuRawUser.0:public at 10.100.0.1

I receive those messages in mrtg.log

2007-09-29 17:34:04 -- Started mrtg with config '/etc/mrtg/fwall1.cfg'
2007-09-29 17:34:04 -- Argument "ssCpuRawUser" isn't numeric in numeric ge 
(>=) at /usr/bin/../lib/mrtg2/BER.pm line 256.
2007-09-29 17:34:04 -- Argument "ssCpuRawUser" isn't numeric in numeric ge 
(>=) at /usr/bin/../lib/mrtg2/BER.pm line 256.
2007-09-29 17:34:04 -- SNMP Error:
Received SNMP response with error code
  error status: noSuchName
  index 2 (OID: 1.3.6.1.4.1.2021.11.0.0)
SNMPv1_Session (remote host: "10.100.0.1" [10.100.0.1].161)
                  community: "public"
                 request ID: 951103521
                PDU bufsize: 8000 bytes
                    timeout: 2s
                    retries: 5
                    backoff: 1)
 at /usr/bin/../lib/mrtg2/SNMP_util.pm line 490
2007-09-29 17:34:04 -- SNMPGET Problem for 
.1.3.6.1.4.1.2021.11.ssCpuRawUser.0 .1.3.6.1.4.1.2021.11.ssCpuRawUser.0 on 
public at 10.100.0.1::::::v4only
 at /usr/bin/mrtg line 2149
2007-09-29 17:34:04 -- 2007-09-29 17:34:04: ERROR: 
Target[server.cpuuser][_IN_] ' $target->[3]{$mode} ' did not eval into 
defined data
2007-09-29 17:34:04 -- 2007-09-29 17:34:04: ERROR: 
Target[server.cpuuser][_OUT_] ' $target->[3]{$mode} ' did not eval into 
defined data

Can you help me
Thanks
Andrea