Unfortunately using fence_ipmilan is not possible to display more debugging details, so as mentioned earlier could you please run ipmitool directly?
ipmitool vv -I lanplus -H c-hv05.prd.sdis38.fr -p 623 -U stonith -P <PASSWORD> -L ADMINISTRATOR chassis power status
Above should display more details ...
root@hv04:/etc# ipmitool -vv -I lanplus -H c-hv05.prd.sdis38.fr -p 623 -U stonith -P 'xxx' -L ADMINISTRATOR chassis power status >> Sending IPMI command payload >> netfn : 0x06 >> command : 0x38 >> data : 0x8e 0x04 >> Sending IPMI command payload >> netfn : 0x06 >> command : 0x38 >> data : 0x8e 0x04 >> Sending IPMI command payload >> netfn : 0x06 >> command : 0x38 >> data : 0x8e 0x04 >> Sending IPMI command payload >> netfn : 0x06 >> command : 0x38 >> data : 0x8e 0x04 >> Sending IPMI command payload >> netfn : 0x06 >> command : 0x38 >> data : 0x0e 0x04 >> Sending IPMI command payload >> netfn : 0x06 >> command : 0x38 >> data : 0x0e 0x04 >> Sending IPMI command payload >> netfn : 0x06 >> command : 0x38 >> data : 0x0e 0x04 >> Sending IPMI command payload >> netfn : 0x06 >> command : 0x38 >> data : 0x0e 0x04 Get Auth Capabilities error Error issuing Get Channel Authentication Capabilities request Error: Unable to establish IPMI v2 / RMCP+ session root@hv04:/etc# -- Nicolas ECARNOT