To be honest, I never got that cmdlet to work correctly.
As an alternative, you can try the Get-EsxCli cmdlet.
Something like this
$esxcli=Get-EsxCli-VMHostMyEsx
$esxcli.system.syslog.config.set(4,512,$null,$false,"192.168.1.100,192.168.1.101:80",$null)$esxcli.system.syslog.reload()
To see the description of the parameters for the set method you can do
$esxcli.system.syslog.config.help("set")